Industrial robot arm

ABSTRACT

A robot arm ( 500 ) for end-effector motion. The robot arm comprises a first actuator ( 4 ) and a first kinematic chain from the first actuator to an end-effector platform, which gives a first degree of freedom for positioning the end-effector platform. The robot arm also comprises a second actuator ( 5; 5   b ) and a second kinematic chain from the second actuator to the end-effector platform, which gives a second degree of freedom for positioning the end-effector platform. The robot arm further comprises a third actuator ( 6; 6   b,    512 ) and a third kinematic chain from the third actuator ( 6; 6   b ) to the end-effector platform, which gives a third degree of freedom for positioning the end-effector platform. The robot arm also comprises a fourth actuator ( 50; 150 ) and a fourth kinematic chain configured to transmit a movement of the fourth actuator to a corresponding orientation axis ( 65 ) for an end-effector ( 28 ). The fourth kinematic chain comprises an orientation linkage ( 52, 57, 59; 202, 204, 207, 209; 284, 286; 251, 256, 258 ) mounted to the inner arm-assemblage via at least one bearing ( 53, 55; 206 ), and an orientation transmission ( 64 B,  64 A,  216; 64 C,  64 D,  64 E;  100, 64 A;  281, 279, 275; 260, 262, 264, 266, 271, 270 ) mounted to the end-effector platform, wherein the orientation linkage comprises an end-effector rotation link ( 59; 209; 258; 281 ) and joints ( 58, 60; 208, 210; 257, 259; 257, 259; 282, 280 ) that provide at least two degrees of freedom for each end joint of the end-effector rotation link.

CROSS-REFERENCE TO RELATED APPLICATION

This application is the National Phase, under 35 U.S.C. § 371(c), ofInternational Application No. PCT/EP2019/050611, filed Jan. 11, 2019,which claims priority from European Application No. EP 18151630.3, filedJan. 15, 2018. The disclosures of all of the referenced applications areincorporated herein by reference in their entirety.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

TECHNICAL FIELD

The present disclosure belongs to the technical field of industrialrobot arms, and in particular to light weight robot arms for very fastprocesses, for extremely fast movements of objects and for high safetyrobot installations.

BACKGROUND

High safety installations are needed for example at direct collaborationbetween human and robot and when it is an advantage to use fencelessrobot installations. Looking at the state of art, there are parallelkinematic robots (as the Delta robot described in WO1987003528A1), whichhave all the actuators mounted on a fixed stand and where it istherefore possible to obtain a light weight structure. However, theseparallel kinematic robots have the disadvantage that the arm systemoccupies a very large space and that the workspace is very small inrelation to the space needed for the arm system. Therefore, these robotscan only be used for applications where a large space is available forthe arm system and where it is enough to have a very restrictedworkspace, especially in the vertical direction. Thus, the Delta robotis mainly used for pick- and place operations above a flat surface suchas a conveyor belt with plenty of space for the robot arm structure.

In the patent application WO2014187486, slim parallel structures areproposed, enabling a larger workspace in relation to the space neededfor the arm system in comparison with for example the Delta robot. Inthis robot structure, a first actuator is driving a first arm about afirst axis, a first kinematic chain is configured to transmit rotationof the first arm to the movement of an end-effector and the firstkinematic chain has a first rod and a first joint between the first armand the first rod. The first joint has at least two degrees of freedom(DOF) and a second joint is mounted between the first rod and theend-effector. To work without losing constraints on the six DOF of theend-effector, the design according to WO2014187486 relies on thetorsional stiffness of the first rod. However, this means that both thefirst joint and the second joint of the first rod must have two DOF andnot more, which in turn means that it will not be possible to obtainconstant tilting angle of the end-effector more than in the middle ofthe workspace. Therefore, the slim robot concept according toWO2014187486 requires a two DOF wrist even in simple pick- and placeoperations over a horizontal surface. However, such a wrist will add asubstantial weight and the robot will not have an as light weight armsystem as for example a Delta robot. Moreover, cabling will be needed totransmit power and to control the actuators of the wrist.

In the patent application WO2015188843, a parallel kinematic robotcomprises a base and an end-effector that is movable in relation to thebase. A first actuator is attached to the base and connected to theend-effector via a first kinematic chain comprising a first arm, a firstrod, a first joint between the first arm and the first rod, and a secondjoint between the first rod and the end-effector. A second actuator isattached to the base and connected to the end-effector via a secondkinematic chain comprising a second arm, a second rod, a third jointbetween the second arm and the second rod, and a fourth joint betweenthe second rod and the end-effector. A third actuator is attached to thebase or to the first arm, and connected to the end-effector via a thirdkinematic chain comprising a first gear wheel and a second gear wheel,the first and second gear wheels being journaled in bearings to theend-effector and intermeshing with each other. At least one element ofthe third kinematic chain constitutes a kinematic pair with at least oneelement of the first kinematic chain. A kinematic chain responsible fora translational movement of the end-effector is thereby utilized as asupport structure for a kinematic chain responsible for a rotationalmovement of the end-effector.

In contrast to the slim structures in WO2014187486, WO2015188843describes a robot structure needing very large space for its arm system.It contains three separate kinematic chains directly connecting threeactuators with the end-effector platform to be moved and thereforesignificant space is needed for three arms swinging in three differentdirections. Moreover, the workspace of the robot structure inWO2015188843 is much smaller than for the robot structure in thisinvention.

WO2015188843 includes an arrangement for rotating a tool mounted on theend-effector platform. The arrangement in FIG. 1 of WO2015188843consists of serially working links and gears. These links are mounted ontwo of the three separate kinematic chains connecting the actuators withthe end-effector platform and restrict the already limited positioningcapability. These restrictions depend on the fact that the links aremounted on two separate kinematic chains, on how the connections of theserially working links are made, and on the fact that the working rangeof the links are reduced significantly when the arms are rotated awayfrom their zero positions. In FIG. 1 of WO2015188843 a rotation of thetool around a first axis will simultaneously rotate the tool around thesecond axis and to compensate for this, the rotation range will be lostfor the second axis. Moreover, the rotation capability will be severelyreduced and achieve a large offset the further the end-effector platformis moved away from the center of the workspace. However, the arrangementin FIG. 2 of WO2015188843 will give large rotation ranges but willreduce the limited workspace even more than the concept described inFIG. 1 of WO2015188843. One reason for this is the need of Cardan jointsin the links between the arms and the end-effector platform. Moreover,several serially connected gear steps are needed in the kinematic chainused to rotate the tool. This will increase arm and end-effectorplatform weight, increase backlash and friction, and increase therequirements on maintenance.

SUMMARY

It is thus an object of the disclosure to alleviate at least some of thedrawbacks with the prior art. It is a further object to provide a lightweight robot arm that is suitable for very fast processes, for extremelyfast movements of objects and/or for high safety robot installations.These objects and others are at least partly achieved by the robot armaccording to the independent claim, and by the embodiments according tothe dependent claims.

According to a first aspect, the disclosure relates to a robot arm forend-effector motion. The robot arm comprises a first actuator configuredto rotate an inner arm-assemblage about a first axis of rotation. Theinner arm-assemblage is connected to an outer arm-linkage pivotablyarranged around a second axis of rotation, and the outer arm-linkage isconnected to an end-effector platform, thereby forming a first kinematicchain from the first actuator to the end-effector platform, which givesa first degree of freedom for positioning the end-effector platform. Therobot arm comprises a second actuator configured to rotate the outerarm-linkage around the second axis of rotation, thereby forming a secondkinematic chain from the second actuator to the end-effector platform,which gives a second degree of freedom for positioning the end-effectorplatform. The robot arm further comprises a third actuator configured torotate a shaft around a third axis of rotation such that the outerarm-linkage is rotated via a joint, thereby forming a third kinematicchain from the third actuator to the end-effector platform, which givesa third degree of freedom for positioning the end-effector platform. Therobot arm also comprises a fourth actuator and a fourth kinematic chainconfigured to transmit a movement of the fourth actuator to acorresponding orientation axis for an end-effector. The fourth kinematicchain comprises an orientation linkage mounted to the innerarm-assemblage via at least one bearing, and an orientation transmissionmounted to the end-effector platform. The orientation linkage comprisesan end-effector rotation link and joints that provide at least twodegrees of freedom for each end joint of the end-effector rotation link.

Thus, the disclosed robot arm is industrially applicable since it hasthe capabilities to keep constant tilt angle of the end-effector,control the tilt angle of the end-effector, control the rotation anglewith constant tilt angle of the end-effector and control both the tiltangle and the rotation of the end-effector, all without including anyactuator in the arm structure. These important features are obtainedsimultaneously with a very slim robot structure and for a very largeworkspace.

According to some embodiments, the orientation transmission comprises aconnection to the end-effector, which gives at least four degrees offreedom for the end-effector motion. Thus, thereby the end-effector canbe moved in at least four degrees of freedom without having any actuatorin the arm structure.

According to some embodiments, the orientation transmission comprises atleast one outer gearing mechanism arranged for rotating the end-effectorwithin an angular range that is determined by the gear ratio of theouter gearing mechanism. Thereby the end-effector may be controlled toobtain a programmed rotation angle when the inner arm-assemblage isarranged to rotate around a vertical axis or a programmed tilt anglewhen the inner arm-assemblage is arranged to rotate around a horizontalaxis.

According to some embodiments, the orientation linkage comprises atleast one inner gearing mechanism arranged for rotating the end-effectorwithin an angular range that is determined by the gear ratio of theinner gearing mechanism, without being limited by the rotation of theouter arm-linkage. Hence, large end-effector reorientations can beprovided in all of the large workspace.

According to some embodiments, the orientation linkage and theorientation transmission are arranged for rotating the end-effectoraround an orientation axis without rotational angular limits. Therebythe end-effector can always be rotated such that the shortest possiblepath (and minimal cycle time) can be chosen.

According to some embodiments, the second kinematic chain comprises theinner arm-linkage including at least one link being connected to theouter-arm linkage via connection bearings, and wherein the secondactuator is configured to move the at least one link via at least oneinner connection joint connected to the at least one link. The secondactuator can therefore be situated at the robot stand, not moving withthe arm structure.

According to some embodiments, the outer arm-linkage comprises an outerpair of parallel links connected to the end-effector platform. The innerarm-linkage comprises an inner pair of parallel links that are connectedto the outer pair of parallel links of the outer arm-linkage. Also, thesecond kinematic chain is configured to transmit the rotation of a leverto a corresponding movement of the end-effector platform. Since theouter pair of parallel links prevents undesired rotation of theend-effector platform, no additional wrist motions (actuators andtransmission that adds cost and weight) are necessary, for instance inthe industrially important case of four degrees of freedom forpick-and-place operations.

According to some embodiments, the outer pair of parallel links and theinner pair of parallel links are connected by means of one connectionbearing for each link connection of the respective links, and where therotation axes of the connection bearings are at a right angle to anaxial centerline of each respective link of the outer pair of parallellinks. Thereby the outer arm-linkage is accurately controlled by theinner arm-linkage without any uncertainty with respect to the kinematicsof the connection points between the links of the inner and outerarm-linkages. The outer arm-linkage is connected via two joints to theinner arm-assemblage such that a line of rotation through the centers ofthese two joints remains vertical (or horizontal, depending on armorientation) during positioning.

According to some embodiments, the robot arm comprises a rigid beamconnecting the connection bearings mechanically with each other. In thisway a more accurate mechanical solution is obtained to transmit thedirection of the rotation axis of the inner arm-assemblage to therotation axis of the end-effector via the serially connected inner andouter arm-linkage. In an alternative embodiment, the bearings of thesecond pair of bearings are connected to each other with a beam parallelto the end-effector beam.

According to some embodiments, the inner pair of parallel links ismounted via ball-and socket joints on offset beams to the rigid beam.Since the geometry of ball- and socket joints can easily be made withvery high accuracy, this further increases the accuracy to transmit thedirection of the rotation axis of the inner arm-assemblage to therotation axis of the end-effector via the serially connected inner andouter arm-linkages.

According to some embodiments, the third kinematic chain comprises aninner transmission connected between the third actuator and an actuatinglink of the outer pair of parallel links. The inner and mostload-carrying part of the robot arm can therefore be made strong butslim, with the inner part of the third kinematic chain well protected.

According to some embodiments, the robot arm comprises a link bearingmounted along the actuating link of the outer pair of parallel links.The rotation axis of the link bearing coincides with a center of theactuating link of the outer pair of parallel links. The link bearing isused in order to avoid any unwanted tilt angle errors of the endeffector caused by the rotation of the inner transmission. Thus, thelink bearing makes it possible to always swing the inner link pair intwo directions with constant end-effector tilt angles.

According to some embodiments, the robot arm comprises end-effectorbearings connecting the outer pair of parallel links and theend-effector platform, where the rotation axes of the end-effectorbearings are perpendicular to the centers of the outer pair of parallellinks. This makes a very slim robot arm structure possible with alight-weight end-effector platform. Because of the end-effectorbearings, the outer arm-linkage will constrain all the six DOFs of theend-effector platform and no more links are needed between the rest ofthe robot structure and the end-effector platform.

According to some embodiments, the rotation axes of the end-effectorbearings are parallel with the rotation axes of the connection bearings.Thereby accurate control is obtained for rotating the tool axis.

According to some embodiments, the robot arm comprises connectionbearings connecting the links of the outer pair of parallel links andthe links of the inner pair of parallel links, where a rotation axis ofeach connection bearing coincides with the center of the respective linkof the outer pair of parallel links. Thereby lower DOFs and therebylower manufacturing costs are obtained for the joint connections betweenthe outer arm-linkage and the inner arm-linkage.

According to some embodiments, the links of the inner pair of parallellinks comprises pairs of parallel links, and these pairs of parallellinks are mounted with ball-and socket joints on each side of the linksof the outer pair of parallel links. This will make it possible tofurther increase the accuracy of the connection between the outerarm-linkage and the inner arm-linkage. Moreover, simpler link- and jointsolutions can be used with pair of sockets.

According to some embodiments, the inner arm-assemblage comprises an armlink that is hollow and a shaft mounted axially with bearings inside thehollow arm link. The shaft is arranged to be rotated by means of thethird actuator. Thereby a very compact inner-arm solution is obtainedwith internal inner transmission for engaging the outer arm-linkage.Moreover, the inner transmission including two bearings will be fullyprotected from the environment. In some embodiments, to rotate therotation line or axis of the bearing pair around an axis perpendicularto the rotation line or axis, the bearing pair may be mounted on theshaft rotating inside the hollow arm link and actuated by a rotaryactuator via a 90 degrees gear.

According to some embodiments, the robot arm comprises a plurality oforientation linkages, each comprising an orientation transmission. Theplurality of orientation linkages is configured such that acorresponding plurality of concentric output shafts can actuate severalend-effector orientations for one or several end-effectors that arearranged onto the end-effector platform. More than one end-effectororientation, such as those actuated by the fourth and the sixthkinematic chains, can therefore actuate very large orientations.

According to some embodiments, the robot arm comprises a plurality oforientation linkages, each with its connected orientation transmission,configured such that each corresponding end-effector orientation isaccomplished for one or several end-effectors that are arranged onto theend-effector platform. Thereby, typical existing robot wrists (withrotational shaft normally coming from motors at the robot elbow) forconventional articulated robots can then be used in case such a heavierdesign suits the application.

According to some embodiments, the robot arm comprises at least twoorientation transmissions mounted to the end-effector platform and wherean outer gearing mechanism of one of the at least two orientationtransmissions is arranged to rotate at least the other one of the atleast two orientation transmissions. Thus, a second wrist motion can beadded in a decoupled and modular way.

According to some embodiments, the robot arm comprises a fifth actuatorand a fifth kinematic chain configured to transmit a movement of thefifth actuator to a corresponding movement of the end-effector arrangedonto the end-effector platform via the at least one other orientationtransmission. In this way simultaneous tool rotation and tilt can beobtained in the whole workspace of the robot arm. The fifth kinematicchain will always be effective in delivering the needed motion of theconnected transmission to obtain the specified end-effector rotation ortilting.

According to some embodiments, the robot arm comprises at least onefurther actuator and at least one further kinematic chain configured totransmit a movement of the at least one further actuator to acorresponding movement of the end-effector arranged onto theend-effector platform, which gives at least six degrees of freedom forthe end-effector motion.

According to some embodiments, the outer gearing mechanism includes afirst gear wheel arranged for rotating the tool in one degree offreedom.

According to some embodiments, the first gear wheel is mounted to theend-effector platform in such a way that the rotation axis of the firstgear wheel is parallel with the first axis of rotation. Thereby theend-effector will always be perpendicular to horizontal planes in theworkspace in a case that the inner arm-assemblage is arranged to rotatearound a vertical axis, and the end-effector will always tilt around ahorizontal axis when the inner arm-assemblage is rotated around ahorizontal axis. These features make the robot arm very useful inapplications for picking, placing, packaging and palletizingapplications.

According to some embodiments, the outer gearing mechanism includes asecond gear wheel, and the first gear wheel is engaged by the secondgear wheel that is arranged to be rotated by a gear link via a leverconnected to the second gear wheel. Thereby a lightweight arrangement isobtained for rotating the tool since the gear wheels, the lever and thegear link can all be manufactured in carbon reinforced epoxy orcomposites. This transmission solution also makes it possible to obtainprescribed rotation range or tilt range of the tool, which is obtainedby selecting suitable ratio between the radii of the second and thefirst gear wheels, the ratio usually selected to be bigger than one (1).To control the rotation of the tool when an end-effector beam of theend-effector platform is vertical and to control one tilting angle ofthe tool when the end-effector beam is horizontal, an outer gearingmechanism such as a gear transmission is used, which may include eitherof a rotary gear transmission or a linear gear transmission. The geartransmission is mounted on the end-effector platform, now including afirst end-effector beam and an optional structure with anotherend-effector beam parallel with the first end-effector beam. In bothcases a first rotary gear wheel is mounted on the other end-effectorbeam via one or more bearings with rotation axes coinciding with thecenter of the another end-effector beam. The first rotary gear wheel ismechanically connected to the tool via a shaft. In one exampleembodiment, a gear link is implemented with a joint of at least two DOFin each end to connect the gear transmission to an actuator via akinematic chain. In the case of a rotary gear transmission, a secondrotary gear wheel, with its rotation axis parallel or coinciding withthe center of the end-effector beam, is connected to the gear link via alever, whereby movements of the gear link will be transformed intorotation of the second rotary gear wheel of the rotary geartransmission. The first rotary gear wheel is forced to rotate by thesecond rotary gear wheel and the diameter of the first rotary gear wheelmay be smaller than the diameter of the second rotary gear wheel.

According to some embodiments, the first gear wheel is engaged by arack, which is arranged to be moved by the gear link connected to therack. In this way a more space efficient gear transmission is obtainedin relation to using a transmission with two gear wheels. This becauseno lever mounted on the second gear wheel is needed and because it ispossible to make a linear rack thinner than a circular gear wheel. Inthe case of a linear gear transmission, a linear gear (i.e. rack, withgear ratio determined by the size of the pinion wheel) is connected tothe gear link via a joint with at least two DOF, whereby movements ofthe gear actuation link will be transformed to rotation of the firstrotary gear wheel of the linear gear transmission. The first rotary gearwheel (acting as a pinion) is forced to rotate by the linear movement ofthe rack and favorably the circumference of the first rotary gear wheelis smaller than the length of the linear gear.

According to some embodiments, the robot arm comprises at least two geartransmissions mounted to the end-effector platform and where a firstgear wheel of a first gear transmission is arranged to rotate at leastone second gear transmission. In this way it will be possible to controlboth the tilting angle and the rotation angle of the end-effector, whichis important in many applications.

According to some embodiments, the at least one second gear transmissionis of rack- and pinion gear transmission type, and where the rack isconnected to a rack bearing with its axis of rotation parallel with themoving direction of the rack. In this way the control of the first geartransmission will be independent of the control of the second geartransmission, meaning that if the tilt angle of the end-effector ischanged by means to the first gear transmission, the rotation angle willnot be changed and vice versa. To control the rotation of theend-effector with two DOF, a first rack- and pinion gear transmission ismounted on the first rotary gear wheel. The linear gear (i.e. rack) isconnected to a second gear link via a rack bearing and a leverarrangement.

According to some embodiments, at least one pinion of the at least onesecond gear transmission is connected to the end-effector to obtain toolrotation. Thereby it is possible to rotate the end-effector with thesecond gear transmission independent of that the first gear transmissionperforms the tilting of the tool and vice versa. In other words, thepinion of the first rack and pinion transmission are connected such thatthe end-effector may be tilted or rotated.

According to some embodiments, at least one rack bearing has its axis ofrotation coinciding with the axis of rotation of the first gear wheel.The rack bearing is here essential in order to make the rotation controlindependent of the tilt control of the end-effector and by mounting theaxis of rotation of the rack bearing coinciding with the rotation axisof the first gear wheel, more accurate mechanical transmission to thesecond gear transmission is obtained. In other words, the rotationcenter of the rack bearing coincides with the rotation center of therotary gear wheel that carries the first rack and pinion transmission.

According to some embodiments, the robot arm comprises one pinion of theat least one second gear transmission that is connected to theend-effector via a right-angle gear. Thereby it will be possible toobtain the control of two tilting angles and one rotation angle of theend-effector. In this way a six axes robot arm is achieved without anyactuators in the arm structure and all actuators mounted fixed to arobot stand.

According to some embodiments, the robot arm comprises one pinion of theat least one second gear transmission that is connected to anend-effector shaft on which the end-effector is mounted via a bearingwith its axis of rotation coinciding with the axis of rotation of theend-effector shaft. In order to obtain a rotation angle via aright-angle gear and simultaneously a tilt angle, the end-effector shaftis mounted on a bearing that is connected to the pinion of the secondgear transmission. The rotating the pinion of the second geartransmission will in this way tilt the bearing, on which theend-effector shaft is mounted.

According to some embodiments, the robot arm comprises one rack- andpinion gear transmission comprising two racks connected via a commonpinion and where the two racks are arranged to move at right anglerelative to each other. Thereby it is possible to actuate two tiltingangles and one rotation angle independent of each other, which meansthat actuating any of the tilting angles or the rotation angle will notchange the other angles. This means that the restricted angular workingranges for the tilting angles and the rotation angle can be fully usedeverywhere in the workspace of the robot arm and independent of theactual tilt- and rotation angles of the end-effector.

According to some embodiments, the robot arm comprises two racks thatare connected to each other via a rack shaft and a rack bearing. Therebya third rack can be rotated by a second rack pinion while connected to afirst rack, which makes the rotation angle of the end-effectorindependent of one of the tilt angles of the end-effector.

According to some embodiments, the rack shaft is arranged to move freelyin an axial through hole of a pinion belonging to another rack-andpinion transmission. Thereby a third rack may be rotated by a secondrack pinion while connected to a first rack, which makes the rotationangle of the end-effector independent of one of the tilt angles of theend-effector.

According to some embodiments, the robot arm comprises at least one rackbearing that is connected to the fifth actuator via a fixed rack- andpinion transmission mounted on the end-effector platform. Thereby asimpler link structure is obtained for the fifth kinematic chain.

According to some embodiments, the rack bearing is connected to the rackof the fixed rack- and pinion transmission. In this way the use of thefixed rack- and pinion in order to simplify the fifth kinematic chainwill still make it possible to perform independent control of the tiltangles and the rotation angle.

According to some embodiments, the pinion of the fixed rack- and piniontransmission includes a lever, on which a gear link is mounted via ajoint of at least two DOF. Thereby an efficient transmission is obtainedfor the fifth kinematic chain, where the working range of theend-effector rotation or rotation angle can be defined by the diameterof the pinion of the fixed rack- and pinion transmission.

According to some embodiments, an actuating link of the outerarm-linkage is connected to the third actuator via a pair of bearings ofwhich the common rotation axis is rotatable around an axis parallel withthe center axis of the inner arm-assemblage. Thereby the robot arm willbe especially suited for applications where high stiffness transmissionis needed for motion of the end-effector in the direction of therotation axis of the first axis. In another embodiment, the gear link isat one end connected to a lever, which is mounted on a bearing with itsrotation axis parallel with the end-effector beam. The lever isconnected to a rotary actuator via two more levers and a link. To rotatethe rotation line or axis of the bearing pair around an axisperpendicular to the rotation line or axis, the bearing pair is in onedesign mounted on a bearing with its rotation axis parallel with thecenter axis of the hollow link of the inner arm-linkage, and a lever isused to rotate the bearing pair around the rotation axis of the bearingon which the bearing pair are mounted. The lever is connected to anactuator via a link with joints at each end.

According to some embodiments, the link transmission includes a rotatingshaft with a lever in one end and where the lever is connected to a gearlink via a joint of at least two DOF. This embodiment is especiallyuseful in applications where a slim inner arm-assemblage is needed,meaning that the robot arm needs to work in a restricted environment.Moreover, this solution will have the highest transmission efficiency tocontrol the rotation angle or any of the tilting angles of theend-effector. In one exemplary embodiment, the gear transmission isconnected to an actuator via a kinematic chain and the gear link is inone end connected to a lever mounted on a second rotary shaft with itsrotation axis parallel with the hollow link of the inner arm-assemblage.

According to a second aspect, the disclosure relates to a robot arm forpositioning an end-effector in three degrees of freedom, with constanttilt angle. The robot arm comprising an end-effector platform arrangedfor receiving the end-effector. The robot arm comprises a first actuatorconfigured to rotate an inner arm-assemblage about a first axis ofrotation. The inner arm-assemblage being connected to an outerarm-linkage pivotably arranged around a second axis of rotation. Theouter arm-linkage comprises an outer pair of parallel links beingconnected via end-effector bearings to the end-effector platform,thereby forming a first kinematic chain from the first actuator to theend-effector platform. The robot arm comprises a second actuatorconfigured to rotate the outer arm-linkage around the second axis ofrotation. The outer-arm linkage being connected via universal jointsincluding connection bearings to an inner arm-linkage comprising aninner pair of parallel links, thereby forming a second kinematic chainfrom the second actuator to the end-effector platform. The robot armalso comprises a third actuator configured to rotate a shaft around athird axis of rotation such that the outer arm-linkage is rotated aroundthe third axis of rotation via an elbow joint, thereby forming a thirdkinematic chain from the third actuator to the end-effector platform.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a robot arm structure according to some embodiments,that enables an end-effector to be actuated to rotate around an axisperpendicular to the horizontal plane.

FIG. 2A illustrates a robot arm structure according to some otherembodiments.

FIG. 2B illustrates a detail of a type of universal joint mounted on therotary shaft of the inner transmission in FIG. 2A.

FIG. 3A illustrates an industrial robot arm according to a firstembodiment that enables an end-effector to be actuated to rotate aroundan axis perpendicular to the horizontal plane.

FIG. 3B illustrates an industrial robot arm according to a secondembodiment, including an alternative gear transmission to rotate theend-effector.

FIG. 3C illustrates an orientation linkage according to someembodiments.

FIG. 3D illustrates a universal joint according to some embodiments.

FIG. 4A illustrates an industrial robot arm according to a thirdembodiment, where the main structure is arranged with a horizontalcommon rotation axis of the rotary actuators.

FIG. 4B illustrates an industrial robot arm according to a variant ofthe third embodiment

FIG. 4C illustrates an industrial robot arm according to another variantof the third embodiment.

FIG. 4D illustrates an alternative embodiment with a belt drive.

FIG. 5A illustrates an industrial robot arm according to a fourthembodiment, where an end effector may be controlled to both rotate andtilt.

FIG. 5B illustrates an alternative embodiment of a rack to tilt an endeffector with two DOF.

FIGS. 6A and 6B illustrate an industrial robot arm according to a fifthembodiment, including a combination of the rack- and pinion concept inFIGS. 5A and 5B with a transmission including right-angle gears andCardan joints to obtain six DOF robot arm with all actuators fixed tothe robot stand.

FIG. 7 illustrates an embodiment with two rack- and pinion arrangementsto be rotated by a gear wheel in order to obtain six DOF with only oneright-angle gear and no Cardan joints.

FIG. 8 illustrates an embodiment with three rack- and pinionarrangements to be rotated by a gear wheel to avoid right angle gearsand Cardan joints in a six DOF robot arm.

FIG. 9A illustrates an industrial robot arm according to a sixthembodiment with an alternative transmission to the rack- and pinionarrangement in FIG. 5.

FIG. 9B illustrates an alternative orientation linkage according to someembodiments.

FIGS. 10A, 10B illustrate an industrial robot arm according to a seventhand eight embodiments with a horizontal common rotation axis of therotary actuators.

FIG. 11 illustrates an embodiment where the rotary actuators arearranged to obtain a common rotation axis without using hollow shaftmotors as illustrated in FIGS. 1-6.

FIG. 12A illustrates an alternative main structure of the industrialrobot arm of FIG. 2A.

FIG. 12B illustrates how linear actuators can be used, in this case in alinkage without having a lever present as in FIG. 12A.

FIG. 13 illustrates an alternative transmission.

FIG. 14A illustrates variations of joint types, permitted joint offsets,and a backhoe mechanism as part of a second kinematic chain.

FIG. 14B illustrates an alternative backhoe configuration that radicallyincreases the workspace of the robot arm.

DETAILED DESCRIPTION

To obtain a light weight robot structure of an industrial robot, theinvention makes use of new combinations of parallel robot structures andtransmissions. The actuators of the robot arm may be mounted on a fixedrobot stand and the heavy weight of the actuators then does not need tobe moved around by the arm structure. An arm structure of the robot maythen be implemented with only light weight components such as carbontubes, carbon gears and carbon bearings. This enables design of therobot with minimum inertia for high speed, acceleration and accelerationderivative. Moreover, when no or less actuators are placed in the armstructure itself, it may be much easier to build a robot that can workin an environment with explosion risks as for example on oil- and gasplatforms and in industries where explosives are handled. It may also beeasier to build robots that can work in harsh environments as foroutdoor handling equipment, tunnel inspection and vehicle cleaningsystems.

The disclosed industrial robot arm solves the problem of how to obtainconstant tilt angles of the end-effector of the industrial robot arm andsimultaneously obtain a slim design of the robot arm. This makes itpossible for the robot arm to perform pick- and place operations withlimited space requirements over a horizontal surface without any addedwrist for the compensation of end-effector tilting errors. Moreover, therobot arm according to the present invention may include up to sixdegrees of freedom (DOF) with all actuators fixed to the stand. Theend-effector may also be referred to as a tool.

For clarity of the following description, we refer to a normal andpreferred arrangement with positioning in x, y and z direction relativeto a robot stand (not shown) of an end-effector platform, which providesa base for tool orientation(s) in one (1) or several DOF. Toolorientations include tool rotation as actuated by some tooltransmission, either around a tool-connecting shaft at the end-effectorplatform or around some axis perpendicular to the tool-connecting shaft,or both for five DOF. For six DOF a tilting tool rotation may be added,or desired tool tilting can form one of axis four or five. In any case,it is highly desirable to have the end-effector platform beingpositioned without a (in this case undesired) tilting motion, therebyseparating tool positioning from tool orientation. In principle, butomitted for clarity, several end-effectors and tool orientationmechanisms/transmission can be attached onto the end-effector platform,for instance pointing at different direction and having different typeof tools mounted, thereby carrying different tools for differentpurposes, and avoiding a need for using tool-exchangers. As will beevident from the following description, the different transmissions fortool orientation can be combined such that all actuators can still befixed to the robot stand. Thus, more than 6 DOF is possible, but forsimplicity not explained in any detail.

The industrial robot arms disclosed herein incorporates a scheme of fouror five axes that, in some embodiments, are always parallel to eachother. The structure can either be mounted in such a way that all theaxes are either vertical or horizontal (or at any other angle) includingone or more of the following:

-   -   In an exemplary embodiment where the axes are vertical, the        obtained movements of the end-effector are such that the        end-effector is always perpendicular to a horizontal surface in        the whole workspace.    -   In an exemplary embodiment where the axes are vertical, the        rotation of the end-effector around a vertical axis may be        controlled via an added link transmission and a gear, whereby        the actuator for the control of the end-effector rotation may be        fixed to the robot stand.    -   In an exemplary embodiment where the axes together with a fifth        axis are horizontal, the structure contains an added link        transmission together with a gear to keep the end-effector        perpendicular to a horizontal surface in the whole workspace.    -   In an exemplary embodiment where the axes together with a fifth        axis are horizontal, the added link transmission together with        the gear may be used to control one tilting angle of the        end-effector in the whole workspace. The actuator for the        control of the tilting angle of the end-effector may be fixed to        the robot stand.    -   In an exemplary embodiment where the axes together with a fifth        axis are horizontal, a second added link transmission together        with a rack- and pinion gear may be used control the rotation of        the end-effector simultaneously with the tilting of the        end-effector. The actuators for the control of the tilting angle        and the rotation angle of the end-effector may be fixed to the        robot stand. Also, with a third link the end-effector may be        controlled to rotate with three DOF.

Moreover, the robot arms according to the embodiments of the presentdisclosure makes possible a slimmer design compared to a robot designaccording to WO2014187486 and WO2015188843, since only two parallellinks are needed in the link structure connecting the end-effectorplatform with the inner arm-assemblage.

In the present disclosure, a robot is defined to comprise a robot armand a robot controller. A robot arm comprises actuators foraccomplishing end-effector movements. The robot controller, or acomputer connected to the robot controller, may comprise a program withinstructions for moving the end-effector according to the program. Therobot controller and/or computer comprises memory and processor, theprogram is saved in the memory. The robot arm is thus a programmablerobot. However, the robot may be of various kinds, for example anindustrial robot or a service robot.

FIG. 1 illustrates a basic embodiment of the robot arm 500, including astructure according to some embodiments to obtain tool rotation, butexcluding tool tilting.

The robot arm comprises a first actuator 4 configured to rotate an innerarm-assemblage 1 about a first axis of rotation 29. The innerarm-assemblage 1 is connected to an outer arm-linkage, here comprisingan actuating link 18. The outer arm linkage is pivotably arranged arounda second axis 40 of rotation. The outer arm-linkage is connected to anend-effector platform 41, thereby forming a first kinematic chain fromthe first actuator to the end-effector platform. This gives a firstdegree of freedom for positioning the end-effector platform, and therebyalso for the end-effector motion.

The robot arm 500 in FIG. 1 also has a second actuator 5 configured torotate the outer arm-linkage around the second axis of rotation 40,thereby forming a second kinematic chain from the second actuator to theend-effector platform. This gives a second degree of freedom forpositioning the end-effector platform. The second kinematic chain may bedesigned in different ways. One possibility is to have a secondkinematic chain of links between the second actuator 5 and the actuatinglink 18. This possibility is exemplified in the FIG. 1 with theactuating link connected to the inner arm-assemblage 1 by a pair ofbearings (rotating around the second axis of rotation 40) that are partof the joint 16, and with a lever 2 mounted on the output shaft of thesecond actuator 5 for rotation about the first axis of rotation 29. Thelever 2 is connected to the actuating link by means of an innerarm-linkage comprising a link 12 with joints 10, 14 in each end.

The joints 10, 14 are depicted as ball-and-socket joints with at leasttwo degrees of freedom, but of course other kinematically equivalentembodiments are possible, as explained below for the end-effectorrotation link (and FIG. 3C).

In other words, the second kinematic chain comprises the inner-armlinkage including the lever 2 and the link 12 that connects to theouter-arm linkage, the outer-arm linkage including the actuating link 18that here (in FIG. 1) is firmly connected to the end-effector platform41 and beam 41A. Thus, the second kinematic chain comprises the innerarm-linkage including at least one link 12 being connected to theouter-arm linkage via connection bearings 14. The second actuator isconfigured to move the at least one link 12 via at least one innerconnection joint 10 connected to the at least one link 12. Anotheralternative for actuating the second degree of freedom is to have thesecond actuator mounted at the end of the inner arm-assemblage 1 withthe rotating shaft of the second actuator in parallel with the secondaxis of rotation 40. This alternative arrangement, with the secondactuator referred to as 5 b, is illustrated with hatched lines since itis not a preferred embodiment because the actuator moves with the armstructure, but it eliminates the need for the inner arm-linkage giving amore compact inner-arm design. In this alternative, the second kinematicchain comprises the mechanical connection with optional transmissionsbetween the rotating second actuator 5 b and the actuating link 18.Thus, the second actuator 5, 5 b moves the end effector platform 41 inone direction, which in combination with the first kinematic chain givesa second degree of freedom for positioning the end-effector platform andthereby also for the end-effector motion.

The robot arm 500 in FIG. 1 also comprises a third actuator 6 configuredto rotate a shaft 3 around a third axis of rotation 33. The thirdactuator 6 is arranged to rotate the shaft 3 around a third axis ofrotation such that the outer arm-linkage is rotated via a joint 161,thereby forming a third kinematic chain from the third actuator to theend-effector platform. This gives a third degree of freedom forpositioning the end-effector platform.

The third kinematic chain can be designed in different ways. Accordingto one example embodiment, a 90 degrees angle wheel (not visible in theFIG. 1 but the same concept as illustrated with reference number 51 foractuating the fourth DOF below) between the output shaft of the thirdactuator 6 and a rotating shaft 3 inside the inner arm-assemblage 1.This shaft 3 will then rotate the actuating link 18 up and down aroundthe rotational axis 33, and thus the end effector platform 41 will moveup and down. Another alternative embodiment is to use the third actuator(in this case 6 b, fixed to the robot stand, illustrated with hatchedlines since it is not a preferred alternative) to rotate the otheractuators (mounted on a shelf 6 c, the second actuator 5 b alternativelyat the end of the inner arm-assemblage 1) around a rotation axis 99perpendicular to the first axis of rotation 29. The rotation axis 99being perpendicular to the rotation axis 29 by definition permits twodifferent arrangements, possibly with dual actuators 6 b arranged torotate around an x and a y axis respectively (assuming axis 29 point inz direction), which can be used to maintain manipulability for theend-effector when the outer arm linkage is stretched all the way in orall the way out (close to or being singular, not allowed in preferredembodiments). In any case, the third kinematic chain comprises the innerarm-assemblage 1 and an outer arm-linkage only consisting of theactuating link 18 attached to the end-effector beam 41A. In total, theembodiment depicted in FIG. 1 will enable a maximally lean arm design,but it will exhibit undesired tilting in most parts of the workspace,and hence further embodiment (FIG. 2 and further) are needed forindustrial applicability.

The robot arm 500 in FIG. 1 also comprises a fourth actuator 50 and afourth kinematic chain. The fourth kinematic chain is configured totransmit a movement of the fourth actuator to a correspondingorientation axis for an end-effector 28. The orientation axis is definedby the shaft 65. The fourth kinematic chain comprises an orientationlinkage 52, 57, 59 mounted to the inner arm-assemblage via at least onebearing 53. The fourth kinematic chain also comprises an orientationtransmission 64B, 64A mounted to the end-effector platform. Theorientation linkage comprises an end-effector rotation link 59 andjoints 58, 60 that provide at least two degrees of freedom for eachend-joint of the end-effector rotation link. In one embodiment, theend-effector rotation link 59 are connected to a joint 58, 60 at eachend of the end-effector rotation link 59, respectively. Of course,joints 58, 60 can be accomplished in several ways that are kinematicallyequivalent to at least two degrees of freedom with at least two degreesof freedom, for instance as depicted in FIG. 3C.

The orientation linkage may be implemented with different linkstructures. In FIG. 1, the fourth actuator 50 is connected to a 90degrees angle gear 51 driving a shaft 52, on which a lever 57 ismounted.

The orientation transmission may also be implemented in different ways,for example by rack and pinion gears or by backhoe linkages. In FIG. 1,the orientation transmission is implemented with an orientationtransmission comprising gear wheels 64A, 64B mounted to the end effectorplatform 41. With the implementations of the orientation linkage andorientation transmissions shown in the FIG. 1, the orientation linkageis mounted to the joint 58 with the lever arm 57 and the orientationtransmission is mounted to the joint 60 via a lever arm 61 mounted onthe gear wheel 64B. Thus, the fourth actuator 50 will, because of thesecond kinematic chain, be able to rotate the gear wheel 64A. This willbe possible even when the first, second and third actuators move the endeffector platform in three different directions, x, y and z. The gearwheel 64A is connected to a shaft 65 rotating in a bearing 67. Theorientation transmission comprises a connection to the end-effector 28,in this embodiment referred to as a shaft 65, which gives at least fourdegrees of freedom for the end-effector motion.

FIG. 2A illustrates a structure of a robot arm 500 included in someembodiments of the disclosure, including the desired constant tool tiltangle, but excluding the fourth kinematic chain for the tool rotation.In other words, this structure makes it possible to move a tool 28 inx-, y- and z-directions while maintaining constant tilt angles. Thethree actuators 4, 5 and 6 have a common vertical rotation axis, herecoinciding with the first axis of rotation 29. The three actuators arearranged to move the tool 28 in such a way that an end-effector beam 41Aof an end-effector platform 41 will always be parallel with the commonrotation axis of the actuators. More in detail, the robot arm 500comprises a first actuator 4 configured to rotate the innerarm-assemblage 1 about the first axis of rotation 29. The firstkinematic chain is here configured to transmit the rotation of the innerarm-assemblage 1 to a corresponding movement of the end-effectorplatform 41, which in FIG. 2A only includes an end-effector beam 41A.Hence, according to the present invention the end-effector platform maybe made much simpler than in the referred prior art, only including abeam instead of a more complex end-effector platform.

The first kinematic chain comprises an outer arm-linkage comprising anouter pair of parallel links 17, 18 that each at one end is connected tothe end-effector platform 41. The first link 17 of the outer pair ofparallel links 17, 18 is connected at its other end to the innerarm-assemblage 1. Here the inner arm-assemblage 1 is designed to swingin a horizontal plane, actuated by the first actuator 4 aligned to thevertical first axis or rotation 29. The inner arm-assemblage 1 carriesthe two parallel links 17 and 18. The two parallel links 17, 18 areconnected at their outer end to a vertical end-effector beam 41A ofend-effector platform 41, which in turn carries a tool 28, in thefigures illustrated as a vacuum gripper, via a shaft 27 protruding fromthe end-effector platform 41, here the end-effector beam 41A. The firstlink 17 of the outer pair of links is connected to the innerarm-assemblage 1 by means of a ball and socket joint 15 via attachmentparts 7A and 7B. The attachment parts 7A, 7B are rigid mechanical partsas for example carbon rods connecting the ball of the joint 15 rigidlywith the inner arm-assemblage 1. The joint 15 could also be implementedas a universal joint with three DOF. In some embodiments, one, severalor all of the joints 9, 10, 13, 14 and 15 are ball and socket joints,cardan or universal joints. In some embodiments, the joint 16 is auniversal joint. In some embodiments, one or both of the joints 19 and20 are hinge joints.

The robot arm 500 in FIG. 2A also comprises a second actuator 5configured to rotate a lever 2 about the first axis of rotation 29. Asecond kinematic chain is configured to transmit the rotation of thelever 2 to a corresponding movement of the end-effector platform 41. Thesecond kinematic chain comprises an inner arm-linkage comprising aninner pair of parallel links 11, 12 connected to the outer arm-linkage,thus connected to, e.g. between the ends, of the outer pair of parallellinks 17, 18. In other words, the second kinematic chain comprises theinner-arm linkage comprising an inner pair of parallel links 11, 12, anda lever 2. The inner pair of parallel links is connected to the leverand to the outer-arm linkage comprising the outer pair of parallel links17, 18. The second actuator 5 is arranged to rotate the lever about thefirst axis of rotation 29. Also, in some embodiments, the outerarm-linkage comprises an outer pair of parallel links 17, 18 connectedto the end-effector platform 41. The second kinematic chain isconfigured to transmit the rotation of the lever 2 to a correspondingmovement of the end-effector platform.

The robot arm 500 further comprises a third actuator 6. A thirdkinematic chain is configured to transmit a movement of the thirdactuator 6 to a corresponding movement of the end-effector platform 41.The third kinematic chain comprises an inner transmission 3, 16, (161,FIG. 1) between the third actuator 6 and the other end of the actuatinglink 18 of the outer arm-linkage. In other words, the third kinematicchain comprises an inner transmission connected between the thirdactuator and an actuating link of the outer pair of parallel links. Theactuating link 18 of the outer arm-linkage is here connected to a rotaryshaft 3 of the inner transmission by means of a type of universal joint16. The rotary shaft 3 is arranged to rotate inside a hollow link 1A ofthe inner arm-assemblage 1, where it is supported by one bearing at eachend (not shown in the figure). The rotary shaft 3 is connected to thethird actuator 6 via a 90 degrees angle gear (not shown in the figure)at the inner end of the hollow link 1A. The outgoing shaft from thethird actuator 6 is assembled through a hollow shaft of the secondactuator 5 to reach the 90 degrees gear. In other words, the robot arm500 comprises an inner arm-assemblage including one link 1A that ishollow, and the inner transmission of the third kinematic chain includesa shaft 3 mounted axially with bearings inside the hollow link 1A. Theshaft 3 is arranged to be rotated by means of the third actuator 6. Byrotating the rotary shaft 3, the parallel links 17 and 18 will swing upand down to obtain vertical movements of the tool 28. In order to swingthe outer arm-linkage in the horizontal plane, the lever 2 is connectedto the outer arm-linkage via the inner arm-linkage. The lever 2 isarranged to be actuated by the second actuator 5 and is connected to thelinks 11 and 12 via a beam 8 and ball- and socket joints 9 and 10. Thejoints 9, 10 are also referred to as inner connection joints. The innerarm-linkage are connected to the outer arm-linkage by means of joints 13and 14, beams 23 and 24 and connection bearings 21 and 22. In oneexample embodiment, the inner pair of parallel links 11, 12 is mountedvia ball- and socket joints 13, 14 on offset beams 23, 24 to a rigidbeam 25. Between the bearings 21 and 22 the beam 25 is connected to thebearings 21, 22, which constrain the end-effector beam 41A of theend-effector platform 41 to always be vertical. Simultaneously, the beam25 can be used to obtain a pre-stress on the connections to the links 17and 18 of the outer arm-linkage, meaning reduced backlash in thebearings 19, 20, 21, 22 and in the joints 15 and 16. That is, thebearings connect at the ends of the links 17, 18 of the outerarm-linkage. Thus, in an example embodiment, the robot arm 500 comprisesthe rigid beam 25 connecting the connection bearings 21, 22 mechanicallywith each other.

The outer arm-linkage is connected to the end-effector beam 41A by meansof the end-effector bearings 19 and 20. Moreover, the end-effectorbearings 19, 20 connects the outer pair of parallel links 17, 18 and theend-effector platform 41, where the rotation axes 36, 37 of theend-effector bearings 19, 20 are perpendicular to the centers of theouter pair of parallel links 17, 18.

To guarantee that the end-effector beam 41A of the end-effector platform41 will have a constant tilt angle such that the tool 28, e.g. a vacuumgripper, will always be able to pick and place items with a verticalangle in relation to the horizontal plane, the design of the robot arm500 may include one or more of the following:

-   -   The common first axis of rotation 29 for the first actuator 4,        the second actuator 5 and the third actuator 6 is vertical.    -   The beam 8 and the mounting of the joints 9 and 10 is assembled        in such a way that axis 30 that goes through the centers of the        joints 9 and 10 is always parallel with the first axis of        rotation 29.    -   The links 11 and 12 have the same length, meaning that the        distance between joints 9 and 13 is the same and the distance        between joints 10 and 14.    -   The distance between joints 13 and 14 is the same as the        distance between joints 9 and 10.    -   The distance between the centers of the joints 15 and 16 is the        same as the distance between the rotation center 36 of the        bearing 19 and the rotation center 37 of the bearing 20.    -   The distance between rotation centers 34 and 35 of the bearings        21 and 22 is the same as the distance between the rotation        centers 36 and 37 of the bearings 19 and 20.    -   The distance between the rotation centers 34 and 35 of the        bearings 21 and 22 is the same as the distance between the        rotation centers of joints 15 and 16.    -   The length of link 17 has the same length as the length of link        18, meaning that the distance between the rotation center of        joint 15 and the rotation center 36 of bearing 19 should be the        same as the distance between a rotation center 33 of the rotary        shaft 3 and a rotation center 37 of bearing 20.    -   The distance between the rotation center 36 of bearing 19 and        the rotation center 34 of bearing 21 is the same as the distance        between the rotation center 37 of bearing 20 and the rotation        center 35 of bearing 22.    -   The bearings 19, 20, 21 and 22 are mounted in such a way that        their axes of rotation 36, 37, 34 and 35 are parallel and at a        right angle to the axes 31 and 32, which are parallel to the        axes 29, 30 and 40. Thus, the rotation axes 36, 37 of the        end-effector bearings 19, 20 are parallel with the rotation axes        34, 35 of the connection bearings 21, 22.    -   Axis 40 goes through the center of joints 15 and 16. The axis 40        is also defined by the centers of bearings 16A and 16B when the        link 18 is horizontal. The axes 34 and 35 are also perpendicular        to the links 17, 18 of the outer arm-linkage. In other words,        the outer arm-linkage (the outer pair of parallel links 17, 18)        and the inner arm-linkage (the inner pair of parallel links 11,        12) are connected by means of one connection bearing 21, 22 for        each link connection of the respective links 11, 12, 17, 18, and        where the rotation axes 34, 35 of the connection bearings 21, 22        are at a right angle to an axial centerline of each respective        link 17, 18 of the outer arm-linkage.

FIG. 2B illustrates a detail of the type of universal joint 16 mountedon the rotary shaft 3 of the first transmission. This joint 16 connectsthe rotary shaft 3 to the actuating link 18 of the outer arm-linkage andmakes the end-effector beam 41A of the end-effector platform 41 to movevertically. The bearings 16A and 16B are symmetrically mounted by meansof pins 16D and 16E on the rotary shaft 3. Since the axis of rotation 40is defined by the common axis of rotation of the bearings 16A and 16B,the actuating link 18 rotates around the axis 33, and the axis ofrotation 40 will also rotate around the axis 33. In more detail, theactuating link 18 of the outer arm-linkage is connected to the thirdactuator 6 via a pair of bearings 16A, 16B of which the common rotationaxis 32 is rotatable around an axis parallel with the center axis of thehollow link of the inner arm-assemblage 1. The rotating outer parts ofthe bearings 16A and 16B are connected to the beam 16H by means of theattachments 16F and 16G. The attachments 16F, 16G are rigid mechanicalstructures such as rods. The attachments 16F, 16G and beam 16H may beimplemented as a solid fork made in carbon reinforced epoxy. Theactuating link 18 is connected to the beam 16H via the bearing 16C,which makes it possible for the actuating link 18 to rotate around itsown axis. The bearing 16C is here referred to as a link bearing 16C.Since this link bearing 16C makes it possible for the actuating link 18to rotate around its own axis, it will be possible to keep the axes 31and 32 vertical in the whole workspace of the tool 28. The link bearing16C can be placed anywhere between joint 16 and the mounting position ofthe bearing 22 to the actuating link 18 of the outer arm-linkage. Thus,in other words, the robot arm comprises a link bearing 16C mounted alongthe actuating link 18 of the outer pair of parallel links 17, 18, wherethe rotation axis of the link bearing 16C coincides with a center of theactuating link 18 of the outer pair of parallel links. This link bearing16C is a differentiating feature in relation to WO2014187486. Thus, therobot arm 500 may in an example embodiment comprising the link bearing16C mounted to the actuating link 18 of the outer arm-linkage betweenthe connection bearing 22 and a connection of the actuating link 18 tothe inner transmission 3, and where the rotation axis of the linkbearing 16C is coinciding with a center of the actuating link 18 of theouter arm-linkage. Another feature is the mounting of the links 17 and18 with bearings 19 and 20 on the end-effector beam 41A of theend-effector platform 41. This makes it possible to build a much slimmerrobot than described in WO2014187486 since only two links 17 and 18 areneeded between the inner arm-assemblage 1 and the end-effector platform41. The end-effector platform 41 here comprises the end-effector beam41A. An end-effector platform may be used for a robot arm with five orsix DOF. The robot described in WO2014187486 needs three links betweenits first arm and end-effector. Further one difference in relation toWO2014187486 is the use of a beam 25 to obtain pre-stress on the links17 and 18. This will also make it possible to use ball- and socketjoints between the outer pair of links 17, 18 and the inner pair oflinks 11, 12. Moreover, the proposal in FIG. 4 of WO2014187486 needs twoarms (linkages) and not only one arm, thus the inner arm-assemblage 1 asin the present disclosure. That is, a robot according to WO2014187486requires much more space for the arm system. The robot structure of thisinvention does not have these shortcomings of WO2014187486 since it canwork with three DOF in the joint connecting the one (and only) innerarm-assemblage (hollow link 1A) corresponding to the first arm inWO2014187486 to the outer arm-link corresponding to the first rod inWO2014187486. Such a solution is not possible in the slim structures ofWO2014187486 since then the end-effector would lose one constraint andnot be controllable with an added degree of freedom between the firstarm and the first rod. In FIG. 4 of WO2014187486 there is a structurethat is not slim and that requires a large space for the arm system, butwhich may have a joint that can have three DOF between the first arm andthe first rod. However, it is not possible to obtain a slim compactrobot structure with the proposed solution in FIG. 4 of WO2014187486because the vertical movements can in that case only be performed by aseparate kinematic chain connected directly to the end-effector platformas in the delta robot case, and thereby requiring lot of space for thearm structure. Hence, the robot structure according to WO2014187486 canonly control three DOF with the actuators fixed to the stand.

It should be mentioned that the bearings 19, 20, 21 and 22 of FIG. 2Acould be replaced by pairs of bearings according to the assembly ofbearings 16A and 16B in FIG. 2B. Vice versa, the bearing pair 16A and16B may be replaced by a single bearing. The use of bearing pairs willgive higher stiffness or makes use of more light weight bearingspossible. Beside ball bearings, also sliding bearings could be used, forexample in carbon.

With the design as described and when the angle between innerarm-assemblage 1 and actuating link 18 is 90 degrees, an infinitesimalrotation of the output shaft of first actuator 4 will move the tool 28sideways in the horizontal plane and an infinitesimal rotation of theoutput shaft of second actuator 5 will move the tool 28 in or out in thehorizontal plane. An infinitesimal rotation of the output shaft of thirdactuator 6 will move the tool 28 up or down. All movements in the wholeworkspace will moreover be made with the axis 32 vertical and the tool28 will have constant tilt angles. Thus, the robot arm 500 will have thesame movement features as the three main axes of a so-called SCARArobot. But in contrast to a SCARA robot, all the actuators 4, 5, 6 canbe fixed to the robot stand (not show) and therefore an extremely lightweight robot arm can be implemented. The robot stand is a rigidmechanical structure, on which the actuators are rigidly mounted. Therobot stand may in this case be made as a fork with one part holdingfirst actuator 4 and another part holding second and third actuators 5and 6. The robot stand can either be rigidly mounted on the floor, on awall or in a ceiling or on another robot arm.

Thus, the disclosure includes a robot arm 500 for positioning anend-effector 28 in three degrees of freedom, with constant tilt angle.This second aspect of the disclosure is disclosed at least in the FIGS.2A, 2B, 3A, 4B, 10A, 10B, 12A, 12B, 14A and 14B, and in the descriptiondescribing these figures, or at least aspects of these figures. Therobot arm comprises the end-effector platform 41 arranged for receivingthe end-effector. The robot arm comprises the first actuator 4configured to rotate an inner arm-assemblage 1 about a first axis ofrotation 29, 29A. The inner arm-assemblage 1 is connected to an outerarm-linkage 17, 18 pivotably arranged around a second axis 40 ofrotation. The outer arm-linkage comprises an outer pair of parallellinks 17, 18 being connected via end-effector bearings 19, 20 to theend-effector platform 41, thereby forming a first kinematic chain fromthe first actuator to the end-effector platform. The robot arm 500 alsocomprises a second actuator 5 configured to rotate the outer arm-linkage17, 18 around the second axis of rotation 40, the outer-arm linkage 17,18 being connected via universal joints including connection bearings21, 22 to an inner arm-linkage comprising an inner pair of parallellinks 11, 12; 811, 812 (811, 812 see FIG. 12B), thereby forming a secondkinematic chain from the second actuator to the end-effector platform.The robot arm 500 also comprises a third actuator 6 configured to rotatea shaft 3 around a third axis of rotation 33 such that the outerarm-linkage 17, 18 is rotated around the third axis of rotation via anelbow joint 161, thereby forming a third kinematic chain from the thirdactuator to the end-effector platform.

According to some embodiments of the second aspect, the end-effectorbearings 19, 20 are hinge joints with rotation axes 36, 37 that areparallel to each other.

According to some embodiments of the second aspect, the elbow joint 161comprises a hinge joint with an elbow rotation axis that intersects withthe second axis of rotation and with the third axis of rotation.

According to some embodiments of the second aspect, the elbow joint 161is connected to an actuating link 18 being the one of the links of theouter pair of parallel links 17, 18 that is connected to the elbow joint161.

According to some embodiments of the second aspect, the actuating link18 is equipped with at least one link bearing 16C mounted along theactuating link for accepting rotation of the actuating link endsrelative to each other.

According to some embodiments of the second aspect, the rotation axis ofthe link bearing 16C coincides with a rotational centerline of theactuating link 18.

According to some embodiments of the second aspect, the second actuator5 is configured to move the inner pair of parallel links 11, 12 viainner connection joints 9, 10 connected to the inner pair of parallellinks 11, 12.

According to some embodiments of the second aspect, the second kinematicchain is configured to transmit the rotation of a lever 2 to acorresponding movement of the end-effector platform 41.

According to some embodiments of the second aspect, the outer pair ofparallel links 17, 18 and the inner pair of parallel links 11, 12 areconnected by means of one connection bearing 21, 22 for each linkconnection of the respective links 11, 17; 12, 18. The rotation axes 34,35; 31 of the connection bearings 21, 22 are at a right angle to arotational centerline along the link for each respective link of theouter pair of parallel links 17, 18.

According to some embodiments of the second aspect, the robot arm 500comprises a rigid beam 25 connecting the connection bearings 21, 22mechanically with each other.

According to some embodiments of the second aspect, the inner pair ofparallel links 11, 12 is mounted via ball- and socket joints 13, 14 onoffset beams 23, 24 to the rigid beam 25.

According to some embodiments of the second aspect, the shaft 3 isconnected between the third actuator 6 and an actuating link 18 of theouter pair of parallel links 17, 18 via the elbow joint 161.

According to some embodiments of the second aspect, the robot armcomprises end-effector bearings 19, 20 connecting the outer pair ofparallel links 17, 18 and the end-effector platform 41. The rotationaxes 36, 37 of the end-effector bearings are perpendicular to therotational centerline of each link of the outer pair of parallel links.

According to some embodiments of the second aspect, the rotation axes36, 37 of the end-effector bearings 19, 20 are parallel with therotation axes 34, 35 of the connection bearings 21, 22.

According to some embodiments of the second aspect, the robot armcomprises connection bearings 21A, 22A (21A in FIG. 3D, 22Acorresponding to 21A but in the connection bearing 22) connecting thelinks of the outer pair of parallel links 17, 18 and the links of theinner pair of parallel links 11, 12. A rotation axis of each connectionbearing 21A, 22A coincides with the rotational centerline of therespective link of the outer pair of parallel links 17, 18.

According to some embodiments of the second aspect, the innerarm-linkage comprises a backhoe mechanism 803, 10B, 802, 8, 9C/10C,805/806 that rotates the outer arm-linkage 804, 17, 18 around the secondaxis of rotation 40, where the backhoe mechanism connects to the outerpair of parallel links 17, 18 via the connection bearings 21, 21 thatpermit rotation around an axis 31 that is parallel with the second axisof rotation 40. See FIGS. 14A, 14B for 803, 10B, 802, 8, 9C/10C,805/806. By proper dimensions that the skilled person can find out fromFIG. 14B, the rotational axis 31 can be placed such that it does notintersect with any of the rotational axes of the two links of the outerpair of parallel links. The backhoe mechanism can be configured (seeFIGS. 14A and 14B) to radically increase the operational range for thesecond kinematic chain, even to more than 180 degrees; a largerworkspace without any singularities can then be provided.

According to some embodiments of the second aspect, the links of theinner pair of parallel links 11, 12 comprises pairs of parallel links11A, 11B; 12A, 12B. Theses pairs of parallel links 11A, 11B; 12A, 12Bare mounted with ball- and socket joints on each side of the links ofthe outer pair of parallel links 17, 18.

According to some embodiments of the second aspect, the innerarm-assemblage 1 comprises an arm link 1A that is hollow and the shaft 3mounted axially with bearings inside the hollow arm link 1A. The shaft 3is arranged to be rotated by means of the third actuator 6.

FIG. 3A illustrates a first embodiment of the robot arm 500 that enablesthe tool 28 to be actuated to rotate around an axis perpendicular to thehorizontal plane. The reference numbers for common features amongst thedifferent embodiments are the same and reference it thus made to theother figures, e.g. FIGS. 1, 2A, and 2B, for their explanation. In thisfirst embodiment, a rotary gear transmission 64A, 64B with a gear factorbigger than one is outlined to obtain the targeted tool rotation. It isalso shown how the rotary gear transmission is actuated via a mechanicaltransmission from a rotary fourth actuator 50 to a lever 61 on thelargest gear wheel 64B of the rotary gear transmission. The robot arm500 in FIG. 3A thus comprises the fourth actuator 50. A fourth kinematicchain is configured to transmit a movement of the fourth actuator 50 toa corresponding movement of a tool 28 mounted to the end-effectorplatform 41, here comprising parts 41A, 68, 69, 70. The fourth kinematicchain comprises an orientation linkage 52, 57 mounted to the innerarm-assemblage 1 via at least one bearing 53, 55. An orientationtransmission 64A, 64B is mounted to the end-effector platform 41 and theorientation linkage is connected to the orientation transmission 64A,64B via an end-effector rotation link 59 with a joint 58, 60 of at leasttwo DOF at each end. FIG. 3A shows one option to obtain also axis fourof a SCARA robot with all actuators fixed mounted on the robot stand.The four actuators 4, 5, 6 and 50 have coinciding rotation shafts alongthe vertical first axis of rotation 29. The output shaft of the fourthactuator 50 goes through the hollow shaft actuator 50 and is connectedto the inner arm-assemblage 1, in the same way the output shaft of thirdactuator 6 goes through the second actuator 5 and controls the rotationof the shaft 3 via a 90 degrees angle gear (not visible in the figure).The second actuator 5 controls the lever 2 and the fourth actuator 50,which is used to rotate the tool 28 around the vertical axis 71, engagesthe shaft 52 by means of the 90 degrees angle gear 51 (the same type asthe one used between third actuator 6 and the shaft 3). In relation toFIG. 2A, there are the following new features in this implementation ofthe robot arm, some also referring to the embodiments in FIG. 1:

-   -   The links 17 and 18 of the outer arm-linkage are connected        directly to the links 11 and 12 of the inner arm-linkage using        universal joints as connection bearings 21, 22. These joints are        identical and illustrated in detail in FIG. 3D. Regarding the        universal joint denoted 21, illustrated in FIG. 3D, the bearing        21A is mounted around the first link 17, having its axis or        rotation coinciding with the center of the link. The bearings        21B and 21C, with its coinciding rotation axes perpendicular to        the rotation axis of bearing 21A, are mounted on the outer ring        of bearing 21A by means of the shafts 21D and 21E. In other        words, the outer arm-linkage and the inner arm-linkage are        connected by means of one connection bearing 21, 22, here        universal joints, for each link connection of the respective        links 11, 12, 17, 18. The rotation axes 34, 35 of these        connection bearings 21, 22 are at a right angle to a respective        link 17, 18 of the outer arm-linkage.    -   The outer rings of the bearings 21B and 21C are then mounted on        the beam 21H using the rods 21F and 21G. The rod 21H is then        mounted on the first link 11. It is also possible to add a        bearing with its rotation center coinciding with the center axis        of first link 11 between the beam 21H and the first link 11 but        this is not necessary. Regarding the universal joint denoted 22,        the bearing 21A is mounted around the actuating link 18, having        its axis or rotation coinciding with the center of the link. In        other words, the connection bearings 21A, 22A connecting the        links 17, 18 of the outer arm-linkage and the links 11, 12 of        the inner arm-linkage, where a rotation axis of each connection        bearing 21A, 22A coincides with the center of the respective        link 17, 18 of the outer-arm linkage.    -   The rod 21H is then mounted on the second link 12. It is also        possible to add a link bearing with its rotation center        coinciding with the center axis of second link 12 between the        beam 21H and the link 12 but this is not necessary. The joints        21 and 22 should be mounted on the links 17 and 18 such that the        distance between the centers of the joints 15 and 21 is the same        as the distance between the centers of joints 16 and 22. In        comparison with the solution in FIG. 1 to connect the inner pair        of links 11, 12 to the outer pair of links 17, 18, this solution        has the advantage that the mechanical system will be not        redundant, making assembly easier. However, simultaneously the        bearing 21A will get a large diameter when large diameter links        are used, and it will be more difficult to replace a bearing 21A        at malfunction. Then, of course, the pre-stress of the links 17        and 18 will not take place. Of course, the connection with the        beam 25 and the bearings 21 and 22 can be used also in the        4-axis robot arm in FIG. 3A.    -   Because of the bearing arrangement in joint 22, the actuating        link 18 is now allowed to rotate around its center axis also to        the right of joint 22, and the link bearing 16C can be placed        anywhere along an actuating-axis centerline along the actuating        link 18, for example at the end of actuating link 18 on the        joint 20 as specifically depicted here in FIG. 3A. More        generally, this actuating-axis centerline may deviate from the        actuating link 18, in theory if it is parallel with the        centerline or bearing 22A (i.e., like bearing 21A but for joint        22, see FIG. 3D), but in practice considering dynamic forces it        should also intersect with rotational axis 33. That is, the        actuating-axis centerline does not necessarily intersect with        rotational axis 40, although it does so in FIG. 3A.    -   To rotate the tool 28 around the axis 71, being the vertical        axis of the tool 28, the lever arm 57 is mounted on the shaft 52        to swing in a vertical plane. In this way the end-effector        rotation link 59 will rotate the gear 64B by means of the lever        61. The gear 64B will in turn rotate the gear 64A (i.e. the gear        wheel or teeth wheel) and with a gear factor bigger than for        example three, it will be possible to rotate the tool 360        degrees and more. Thus, the gear transmission 64A, 64B may        include a first gear wheel 64A arranged for rotating the tool 28        in one degree of freedom. The shaft 52 is mounted through the        bearings 53 and 55, which in turn are mounted by means of the        rods 54 and 56 on the inner arm-assemblage 1. The lever arm 57        is favorably mounted on the shaft 52 at a right angle and        end-effector rotation link 59 is mounted on the arm 57 with a        ball- and socket joint 58. In its other end the end-effector        rotation link 59 is mounted on the lever 61 also with a ball and        socket joint 60. In other words, the robot arm 500 comprises an        orientation transmission 64A, 64B, 100, 270, 271 including a        second gear wheel 64B, and the first gear wheel 64A is engaged        by the second gear wheel 64B which is arranged to be rotated by        the end-effector rotation link 59 via a lever 61 connected to        the second gear wheel 64B. Of course, all ball- and socket        joints in the figures can be replaced by universal joints of two        or three DOFs, even if such implementations often require more        space and weight. The second gear wheel 64B is mounted on the        outer ring of the bearing 63, which in turn is mounted with its        inner ring on the vertical shaft 62, mounted on the end-effector        beam 41A. The second gear wheel 64B engages the smaller first        gear wheel 64A, which is mounted on the vertical shaft 65,        arranged axially through the beam 68 that is hollow. The shaft        65 is thus rotatably arranged inside the hollow beam 68. Thus,        in other words, the first gear wheel 64A is mounted to the        end-effector platform 41 in such a way that the rotation axis 71        of the first gear wheel 64A is parallel with the first axis of        rotation 29. The shaft 65 is supported by the bearings 66 and        67, which in turn are mounted on the beam 68. The beam 68 is        mounted on the end-effector beam 41A by means on the rods 69 and        70. At the end of the rotating shaft 65 the tool 28 is mounted,        either manually screwed to an end flange (on shaft 65, not        shown) or by means of a tool exchanger on that end flange such        that tool replacement can be automated.

The same kinematic requirements as in FIGS. 1 to 2B are valid whenapplicable in FIG. 3A. For example, all the axes 29, 30, 31, 32 and 40should be parallel and vertical and for FIG. 3A this is also requiredfor axis 71, which is defined by the rotation center of the shaft 65.The links 17 and 18 of the outer pair of links should be parallel and ofthe same length and the same for the links 11 and 12 of the inner pairof links. Notice that joint 9 (FIG. 2A) and part of first link 11 arehidden behind the inner arm-assemblage 1 in FIG. 3A. In WO201418748there is no solution to obtain tool rotation. FIG. 1 in WO2015188843includes an arrangement for rotating a tool mounted on the end-effectorplatform of a robot with three arms. This robot arm system needs a hugespace and the 4:th axis is implemented to tilt the tool. The toolrotation is here made with a separate rotating actuator mounted on thewrist. Moreover, the workspace of the robot is very small and it isfurther reduced by the transmission to the wrist axes. In the solutionof FIGS. 1 and 3A of this disclosure, the rotating shaft 3 with thelever arm 57 connected to the lever arm 61 via the end-effector rotationlink 59 makes it possible to have full working area of the fourth axisin the whole positioning workspace of the robot arm. This is notpossible with the transmission type for axis four in WO2015188843 sincehere the transmission working range will get an increasing offset thefurther the wrist is moved away from the center of the workspace.Another problem with the transmission solution in FIG. 1 of WO2015188843is that the gears needed in the wrist will be close to the motor foraxis six and thus to the tool, giving a clumsy end-effector platform,meaning accessibility problems. As can be seen from FIG. 1 and FIG. 3,the bearings are far away from the tool, thanks to the design of therobot arm with the beam 68 always vertical and separating the gear sidefrom the tool side.

Thus, in the present disclosure the restrictions of WO2015188843 areavoided by mounting two serially working transmissions for toolrotation, thus the orientation linkage and the orientation transmission,on one kinematic chain only and by using a fourth actuator 50 connectedto a gear transmission 64A, 64B on the end-effector platform 41 via asecond rotating shaft 52 with a lever arm 57 connected to the geartransmission via an end-effector rotation link 59 with joints of atleast 2 DOF e.g. in each end, whereby optimal transmission efficiency isobtained between the fourth actuator 50 and the orientationtransmissions 64A, 64B. Moreover, two versions of orientationtransmissions are introduced, one with gear wheels and one with a rack-and pinion, both able to obtain tool rotation capability of +/−180degrees.

FIG. 3B illustrates a robot arm 500 according to a second embodiment,including an alternative orientation transmission to rotate the tool 28compared to the transmission in FIGS. 1 and 3A. In this embodiment arack- and pinion transmission 100, 64A is used, where the gear wheel 64Ain the shape of a pinion rotates the tool 28. A rack 100 of thetransmission 100, 64A is moved by an end-effector rotation link 59,connected to a fourth actuator 50 via a mechanical transmission. Inother words, a first gear wheel 64A is engaged by a rack 100, which isarranged to be moved by the end-effector rotation link 59 connected tothe rack 100. The basic 3 DOFs robot structure with the beam 25 and thebearings 21 and 22 is the same as in FIG. 1 and the transmission fortool rotation with the shaft 52, the lever arm 57 and the end-effectorrotation link 59 is the same as in FIGS. 1 and 3A. The new part in thisimplementation is that the rotating gear wheel 64B in FIGS. 1 and 3A hasbeen replaced by a linear gear, the rack 100, to obtain a rack- andpinion transmission. The linear gear is moved by the end-effectorrotation link 59 via the ball-and socket joint 60. The rack gear ismoved in a linear bearing, outlined by references 101 and 102, which ismounted on the rod 69 via the rod 103. As in FIGS. 1 and 3A, the rod 69together with the rod 70 are used to mount the beam 68 on theend-effector beam 41A of the end-effector platform 41. Also, as in FIGS.1 and 3A, the pinion gear wheel 64A is mounted on the rotating shaft 65to rotate the tool 28.

The advantage of using the rack- and pinion solution in FIG. 3B inrelation to the gear wheel solution in FIGS. 1 and 3A is that it will bepossible, in the workspace, to keep the end-effector rotation link 59closer to the vertical plane defined by the parallel links 17 and 18 ofthe outer pair of links. This will further increase the efficiency ofthe transmission between the rotation of the shaft 52 and the shaft 65.Moreover, this solution will give a somewhat slimmer end-effectorplatform arrangement.

FIG. 3C illustrates an orientation linkage according to someembodiments. This orientation linkage illustrates that it is possible todistribute the degrees of freedom of the joints 58 and 60 into the lever57, the link 59 and the lever 61. Thus, the bearing 58A is mounted inthe lever 57 with a rotation axis coinciding with the center axis of thelever 57, the bearing 58B is mounted with its rotation axisperpendicular to that of bearing 58A and the bearing 58C is mounted withits rotation axis coinciding with the center axis of the link 59. Thebearing 60A is perpendicular to the center axis of the link 59 and thebearing 60B coincides with the center axis of lever 57.

FIGS. 1 to 3D illustrate how the robot arm 500 can be designed to obtainthe same motion features as a SCARA robot but with much lower inertia ofthe arm structure since all the actuators are fixed to the robot stand.

FIG. 4A, illustrating a third embodiment of the robot arm 500, it isshown that the robot arm can also be implemented as an articulated robotarm reaching objects from above. This means that the structure of therobot arm will instead of swinging in a horizontal plane, swings in avertical plane. This means that all the axes that had to be vertical inFIGS. 1 to 3 will now have to be horizontal. However, most of the designfeatures from FIGS. 1 to 3 can still be used. Thus, looking at FIG. 4A,the only new design principles to be exemplified besides working withhorizontal instead of vertical axes 29, 30, 31, 32, 40 and 71, are forthe transmission to the gear wheel 64B. Of course, the same transmissionprinciple as in FIGS. 1 and 3A can also be used in this case and thetransmission principle of FIG. 4A can also be used in FIGS. 1 and 3A.

Looking at the actuators, the hollow shaft actuator of FIG. 4A, i.e. thesecond actuator 5, is arranged to swing the lever 2 to swing the outerpair of links 17 and 18 in and out, the third actuator 6 with its outputshaft going through second actuator 5, is arranged to rotate the shaft 3via a 90 degrees gear to swing the outer pair of links 17 and 18sideways. The first actuator 4 with the output shaft going through afourth actuator 150 is arranged to swing the inner arm-assemblage 1 andthus the outer pair of links 17 and 18 up and down. The new feature forthis embodiment of the robot arm 500 in FIG. 4A is an alternative fourthactuator 150, a hollow shaft actuator which is arranged to swing a firstlever 200. This first lever 200 is connected to the rotating gear 64B bytwo links 202 and 209, included in an orientation linkage. One link 202is in one end mounted with a bearing 201 on the lever 200 and withanother bearing 203 on a second lever 204. The second lever 204 ismounted on the outer ring of bearing 206, which in turn is mounted withits inner ring on the inner arm-assemblage 1 via the protrusion 205. Onthe outer ring of bearing 206 is also a third lever 207 mounted, in sucha way that when the tip of the second lever 204 moves in a horizontaldirection, the tip of the third lever 207 moves in a vertical direction.The rotation axis of the bearing 206 coincides with the axis 40, whichgives the simpler kinematics for the transmission to the gear wheel 64B.The tip of the third lever 207 is connected to the other link 209 viathe ball- and socket joint 208 and the other end of the other link 209is connected to a fourth lever 211 via the ball- and socket joint 210.It should be noted that the bearings 201 and 203 could be replaced byball and socket joints. Now, when swinging the first lever 200, thefourth lever 211 will swing up and down (vertically) and the gear wheels64A, 64B will rotate back and forth, around their axes of rotation,along with the vertical swinging of the fourth lever 211. In this figurethe second gear wheel 64B is mounted on the end-effector beam 41A viathe shaft 213 and the bearing 214. To keep a constant tilt angle of thetool 28 or in order to control the tilt angle of the tool 28 to atargeted angle, a rotary gear transmission 64A, 64B on the end-effectorplatform 41 is used here as in FIGS. 1 and 3A. However, the gear wheelsof the transmission are here vertically arranged, instead ofhorizontally as in FIGS. 1 and 3A. Thus, the rotary gear transmission64A, 64B is controlled by the rotary fourth actuator 150 via anarrangement of the links 202, 209 and the levers 200, 204, 207. As inFIGS. 1 and 3A, rotating the second gear wheel 64B will rotate the firstgear wheel 64A with a gear magnification ratio. First gear wheel 64A ismounted on the beam 68 via the shaft 65 and bearing 66. Rotating firstgear wheel 64A implies that a shaft 216 holding gear wheel 64A rotatesand the tool 27, 28 arranged on the shaft 216 will change its tilt angle(the shaft 216 is here the connection to the end effector). This will beuseful, for example when picking and placing objects at different tiltconditions. It will also be used to keep constant tilt angle all overthe workspace, for example when picking objects from a conveyor.

FIG. 4B illustrates a robot arm according to a variant of the thirdembodiment. With this variant, it is possible to increase the workingrange of the transmission between the levers 200 and 211, in comparisonwith the embodiment illustrated in FIG. 4A. Using the solution in FIG.4B, the gear ratio of the gear transmission 64B-64A can be reduced andthe rotation capability of the gearwheel 64B will be increased in theinner and outer parts of the work space of the robot arm. Here, an innergearing mechanism comprising a backhoe linkage has been introduced,comprising an extra lever 501, which is longer than the lever 204. Thelevers 501 and 204 are connected by the link 505 with the bearings 503and 203 at its ends. When the actuator 150 swings the lever 200, thelink 202 with its bearings 201 and 506 in its ends, will swing the lever501 around the bearing 502, which is mounted on the beam 504. By meansof the backhoe principle the angular rotation of lever 204 will belarger than that of the lever 501 and the gear wheel 64B will get largerrotations than in the direct transmission in FIG. 4A. Thus, in otherwords, the inner gearing mechanism is arranged according to the backhoeprinciple for rotating the end-effector 28 within an angular range thatis determined by the gear ratio of the inner gearing mechanism withoutbeing limited by the rotation of the outer arm-linkage. That is, withoutthe backhoe, enabling a large angular range for the second degree offreedom easily leads to an undesired limitation of the working range ofthe fourth degree of freedom for large orientations around axis 40. Thisis avoided with the backhoe, which is a well-known mechanism forexcavators and various types of cranes. As such, the standard backhoeprinciple can be applied to almost any lever-and-rod linkages within thepresent invention, which for brevity is not further commented ordepicted. In comparison with FIG. 4A, the bearing 206 in FIG. 4B has anoffset from the axis 40, which is of course not necessary but could makethe mechanical design more efficient concerning forces and/or workspace.

In FIG. 4B there are thus two (2) steps with different principles toincrease the magnification of the rotation ratio between the actuator150 and the gear wheel 64A. Of course, the orientation transmission withthe lever 211 and the gears 64A and 64B can also be used where thebackhoe is implemented in FIG. 4B and vice versa. The same concept canbe used for the transmission between actuator 150 and gear wheel 64A inFIG. 5A and between lever 351 and lever 362 in FIG. 10B (with notationsas in FIG. 3D).

FIG. 4C illustrates a robot arm according to another variant of thethird embodiment. According to this another variant, the actuators 4, 5,6 and 150 are mounted on a bracket 510, which can be rotated by anactuator 512 connected to the bracket 510 by the shaft 511. The centerline of the shaft 511 is at a right angle to the center line of theactuators 4, 5 6 and 150. Using the actuator 511, the agility of therobot arm will be increased and since the actuators 4, 5, 6 and 150 forthe control of the robot arm are all located close to each other, themass inertia to be rotated by actuator 512 will be small. Thus, thetorque and power needed for actuator 512 will be much lower than for aconventional serial robot with the actuators distributed in the robotarm. It should also be mentioned that the bracket 510, according to oneembodiment, can be mounted on a linear actuator to increase the workspace. FIG. 4C also shows the option to use an actuator 514 for rotationof the tool 28. When the robot arm handles small objects with very lowmass inertia, the actuator 514 will be lightweight and this solutioncould be an advantage because of lower mechanical complexity than thesolution in FIG. 8 for rotation of the tool.

FIG. 4D illustrates an alternative solution with a belt drive, fortransferring motion to the tool 28, where the gear wheel 64B of FIG. 4Chas been replaced by a belt wheel 64C, and the gear wheel 6A has beenreplaced with another smaller belt wheel 64 E. A belt 64D connects thetwo belt wheels. Such a belt transmission can also replace the backhoemechanism. Instead of belts also wires can be used between two wheels.

Generally, a link is used to transfer a force, and a lever is used totransfer a torque.

Instead of the gear wheel transmission 64A, 64B a rack-and pinionsolution as in FIG. 3B can of course be used. Then the direction of themounting of the rack could be as in FIG. 3B or with a right angle to theplane formed by the outer pair of links 17, 18.

In WO201418748 there is no solution to obtain an articulated robotreaching objects from above and no solution is shown to obtain a fourthaxis to be able to tilt the tool or keep the tool tilting anglesconstant.

In several applications, there are requirements to both tilt and rotatethe tool 28. One possibility for this is to mount a small actuator on ashaft 27 connected to the tool 28 in e.g. FIG. 4A to rotate the tool 28.This will add inertia and electrical wiring to the arm structure and toavoid this, a transmission solution with rack- and pinion is used asillustrated in FIG. 5A. The shaft 27 is then the connection to theend-effector. FIG. 5A illustrates the robot arm 500 according to afourth embodiment, where the tool 28 is controlled to both rotate andtilt or to tilt with two DOF. In FIG. 5A, for efficient tool rotationwith two DOF, a rack- and pinion arrangement 270, 271 is mounted to arotating first gear wheel 64A and a rack 271 is connected to atransmission arrangement 264, 266 via a bearing 267 with its center ofrotation coinciding with the center of rotation of the first gear wheel64A carrying the rack- and pinion arrangement 270, 271. Implementingthese features makes it possible to rotate the tool around two axes 90degrees in relation to each other with +/−180 degrees. This is notpossible with the arrangement described in FIG. 1 in WO2015188843. Inmore detail, the rack- and pinion gear 270 is connected to the tool 28and is arranged to be rotated by the rotary gear transmission 64A, 64B,and the rack 271 of the rack- and pinion gear is moved via a bearing 267and an arrangement of links 258, 264, 266 and levers 256, 260, 262.

The first gear wheel 64A is actuated in the same way as described forFIG. 4A but the first gear wheel 64A is now rotating the linear bearingassembly 270, 271, in which the rack 271 is sliding parallel to therotation axis of gear wheel 64A. Thus, the robot arm 500 comprises atleast two orientation transmissions 64A, 64B; 270, 271; 293, 294; 315,316; 311, 312, 313 (see other figures too) mounted to the end-effectorplatform 41, comprising parts 41A, 68, 69, 70, and similar depending onembodiment of the orientation. A first gear wheel 64A of an orientationtransmission is arranged to rotate at least one other orientationtransmission 270, 271; 293, 294; 315, 316; 311, 312, 313 (see otherfigures too). As in FIG. 3B, the rack rotates the pinion gear, in thiscase denoted 270, to rotate the tool 28 via the shaft 65A (correspondingto 65 in FIG. 3B). In other words, at least one pinion 270, 294, 316 ofthe at least one other orientation transmission 270, 271; 293, 294; 315,316; 311, 312, 313 is connected to the tool 28 to obtain tool rotation.In some embodiments, the robot arm comprises at least two orientationtransmissions 64A, 64B; 270, 271; 293, 294; 315, 316; 311, 312, 313mounted to the end-effector platform 41 and where an outer gearingmechanism 64B, 64A; 64C, 64D, 64E; 100, 64A; 271, 270 of one of the atleast two orientation transmissions is arranged to rotate at least theother one of the at least two orientation transmissions 270, 271; 293,294; 315, 316; 311, 312, 313.

The sliding movement of the rack 271 is accomplished by the bent rod 266via the bearing 267. The bearing 267 should preferably have its axis ofrotation coinciding with the axis of rotation of the gear wheel 64A.Then the linear bearing assembly 270, 271 can be rotated by the gearwheel 64A without any rotation or translation of the bent rod 266. Inother words, at least one rack bearing 267 has its axis of rotation 71coinciding with the axis of rotation 71 of the first gear wheel 64A.

The bent rod 266 is moved by the link 264 via the ball- and socket joint265. The link 264 is mounted on the lever 262 via the bearing 263. Abearing 261 is mounted with its inner ring on the beam 269, which inturn is mounted on the shaft 62 coming out from the inner ring of thebearing 63 of the gear wheel 64B. The shaft 62 is mounted on theend-effector beam 41. The lever 260 is mounted on the outer ring of thebearing 261 as is also the case with the lever 262. When the tip oflever 260 is moved vertically, the tip of lever 263 moves horizontally,compare the arrangement with the previously described levers 204 and207. The vertical movements of the tip of lever 260 are obtained fromthe vertical movements of the tip of lever 256 via the gear link 258.The gear link 258 is mounted with ball- and socket joints 257 and 259 onthe tips of the levers 256 and 260. The lever 256 is mounted with about90 degrees angle on the rotating shaft 261, compare the arrangement forthe lever 57 in FIGS. 1 and 3B. Thus, rotating the shaft 251 will swingthe lever 256 up and down and via the gear link 258, the two levers 260and 262, the link 264, the rod 266 and the bearing 267, and move therack gear 271 back and forth, giving rotations of the tool 28 at atilting direction determined by the rotation angle of the gear wheel64A. In other words, the robot arm 500 comprises an orientation linkage251, 258, 264 including the rotating shaft 251 with the lever 256 in oneend and where the lever 256 is connected to the gear link 258 via thejoint 257 of at least two DOF. The shaft 251 is mounted on the bearings253A and 253B. The bearing 253A is mounted on the inner arm-assemblage 1via the beam 255 and the bearing 253B is mounted on the innerarm-assemblage via the shaft 269 of the bearing 206. The shaft 269 forbearing 253B is mounted on the inner arm-assemblage 1 via the protrusion205. In the figure, the shaft 251 is arranged to be rotated by a fifthactuator 250. Thus, the robot arm 500 comprises a fifth kinematic chainconfigured to transmit a movement of the fifth actuator 250 to acorresponding movement of the tool 28 mounted to the end-effectorplatform 41 via the outer gearing mechanism, here comprising a firstgear wheel 64A. The fifth kinematic chain comprises at least one rackbearing 267, 297 connected to the fifth actuator 250 via an orientationlinkage 251, 258, 264. However, a fifth actuator with its axis ofrotation coinciding with the first axis of rotation 29 could be used,connecting the shaft 251 to the fifth actuator via a 90 degrees anglegear as shown in FIGS. 1 and 3B. Of course, also a transmission chainarrangement as the one used for the rotation of the gear wheel 64B byfourth actuator 150 could be used to move the lever 260 up and down. Thelink chain arrangement for the rotation of the tool 28 can of coursealso be placed on the other side of the inner arm-assemblage 1 and thenthe linear bearing arrangement 270, 271 will be mounted on the shaft 65to the left of the bearing 66 instead, making it possible to design amore compact solution. Moreover, the whole rack- and pinion arrangementcould be placed to the left of the gear wheel 64A, but for the clarityof the figure this more compact solution is not shown. It is alsopossible to replace the gear wheel transmission 64A, 64B with a rack-and pinion arrangement as in FIG. 3B.

The transmission from actuator 150 to the lever mounted on gear 64B isdifferent from the transmission from actuator 250 to the lever 260.However, it is possible to use the same transmission concepts in bothcases. When the transmission concept used between the actuator 150 andthe lever mounted on gear 64B is used, the backhoe linkage can beincluded. The same transmission concept as used between actuator 250 andthe lever 260 in FIG. 5A is also used in the FIGS. 6A, 9 and 10A as willbe illustrated in the following. Of course, these transmissions can bereplaced by the type of transmission used from actuator 150 to the levermounted on gear 64B in FIG. 5A and they can include the backhoe linkagedescribed in FIG. 4B.

In FIG. 5B, illustrating an alternative embodiment of the rack 271, therack 271 has been rotated 90 degrees, whereby the teeth point downwards.The connected pinion 270 now has a horizontal rotation axis and theshaft 65 is horizontal. The tool 28 is mounted at a right angle to theshaft 65A. As in FIG. 5A, the linear bearing assembly 273 for the rack270 is mounted on the gear wheel 64A and the bearing 267 between therack 271 and the transmission part 266 has its center of rotationcoinciding with the center of rotation of the gear wheel 64A. Thismounting of the rack- and pinion results in the possibility to controlboth tilting angles of the tool 28.

So far solutions for five axes robot control with all actuators fixed tothe robot stand have been shown. To obtain six DOF, one solution is touse transmissions with rotating shafts, Cardan joints and 90 degreesgears as shown in FIGS. 6A and 6B.

FIGS. 6A and 6B illustrate a robot arm 500 according to a fifthembodiment, including a combination of the rack- and pinion conceptaccording to FIGS. 5A and 5B, with a transmission including right-anglegears and Cardan joints 282, 280 is used to accomplish one furtherkinematic chain. That is, this one further kinematic chain is configuredto transmit a movement from actuator 285 to a respective movement of theend-effector arranged onto the end-effector platform, which gives atleast six degrees of freedom for the end-effector motion, still with allactuators fixed to the robot stand.

The robot arm 500 has here been split up in two figures in order to beable to illustrate in greater detail. FIG. 6A illustrates thetransmission from a rotating actuator 285 with its right-angle geartransmission 299 to the horizontally rotating shaft 275 on theend-effector platform 41. To make this possible, the output from theright-angle gear transmission 299 rotates the shaft 284, which ismounted on the inner arm-assemblage 1 (mounting not shown). The shaft284 engages the right-angle gear 283, the output of which is connectedto a first Cardan joint 282 via a link 286, the first Cardan joint beingmounted to have its center on the line 40. The output of the Cardanjoint 282 rotates the shaft 281, which in its other end is connected toa second Cardan joint 280, via a link 279, the second Cardan joint 280with its center on the axis 32. The output of the second Cardan joint280 drives the right-angle gear 278, which in turn rotates the shaft275. The shaft 275 is mounted with bearings inside the beam 68 and canfreely rotate inside the bearing 66, which supports the first gear wheel64A via the hollow shaft 65. The shaft 275 is also arranged to freelyrotate inside the shaft 65 and the first gear wheel 64A. Thus, anorientation linkage comprising 284 and 286, and the orientationtransmission comprising 281, 279 and 275, are arranged for rotating theend-effector around an orientation axis 71, which will be withoutrotational angular limits due to the free rotation inside shaft 65 andelsewhere is without stop.

FIG. 6B illustrates that the shaft 275 is connected to the right-anglegear 277, which on its output rotates the shaft 65B that can freelyrotate inside the bearing of the pinion 290. The shaft 65B is connectedto the last right-angle gear 288, which on its output is connected tothe shaft 65C rotating the tool 28. Thus, the connection to theend-effector here comprises the shaft 65C. Also, one pinion 270 of theat least one second gear transmission 270/271 is connected to the tool28 via a right-angle gear 288. The shaft 65C is connected to the pinion270 via the bearing 291 and the beam 290. As in FIGS. 5A and 5B therack- and pinion 270, 271 is arranged to be rotated by the first gearwheel 64A. The rotation centers of the output gear wheel of theright-angle gear 278, the shaft 275 and the input gear wheel of theright-angle gear 277 are on the common axis 71. The rack 271 is moved bythe link 264, connected to the rack 271 via the beam 266, the rackbearing 267 and the rack attachment 287. As in FIG. 5A, the link 264 isconnected to a link arrangement via a lever 262.

As can be seen from FIG. 6A, five right-angle gears and two Cardanjoints are needed to obtain tool 28 rotation from the actuator 285 fixedto the robot stand. The advantage of this solution is the possibility toobtain infinite tool rotation angles and the disadvantage is the loss ofpositioning workspace because of the working range limitations of theCardan joints 280 and 282.

By observing that shaft 275, in FIG. 6A, is a straight shaft (with sometype of bearings 66) that is open at both ends, the skilled person willnotice the similarity to outer robot arm segments of robots according tomany existing products. This points directly at making shaft 275 hollowwith other bearings 66 and another shaft 275 inside, and so on for aplurality of concentric shafts. It is common practice in the art to havethree such concentric shafts. Such a plurality of concentric shafts 275entering into the example wrist mechanism shown in FIG. 6B can then beused either for extending/revising that mechanism (in a variety of ways,not considered here), or for mounting an existing standard robot wristinto the positioning of the new end-effector platform according to thepresent disclosure. Considering the other end of the concentric shafts275, with inner shafts protruding further out (to the left alongcenterline 71 in FIG. 6B), and for each shaft adding another right-anglegear 278, the remaining part (from right-angle gear 278 up to actuator285) of the sixth kinematic chain can be duplicated, it follows that aplurality of kinematic chains can be added. The robot arm then comprisesa plurality of orientation linkages 284, 286, each comprising anorientation transmission 281, 279, 275.

Furthermore, as another variation that the skilled person would find,the plurality of orientation linkages can be configured such that acorresponding plurality of concentric output shafts 275 can actuateseveral end-effector orientations not only for one but also for severalend-effectors that are arranged onto the end-effector platform, forinstance in different directions, or next to each other. Since manystandard articulated robots, as indicated above, have wrist motorsarranged at the back of their out arm link, with shafts in parallel orconcentrically going through the outer-arm link to a wrist with 2 or 3DOF, there is the option with the present invention to combine a 3 DOFSCARA-like motion according to FIG. 2A with a standard 3DOF robot wrist(instead of the mechanism shown in FIG. 6B, to use existingcomponents/interfaces) that is actuated by a plurality of shafts 275driven by a plurality of motors 285 that all are fixed to the robotstand. Arranging shafts 275 on a standard SCARA robot would requirecostly and heavy telescopic shafts to deal with the vertical placementof the wrist (and no useful 6 DOF SCARA exists), which contrasts withthe present invention where the properties of the third kinematic chainenables a leaner solution.

FIG. 7 illustrates an alternative example embodiment of the rack-andpinion arrangement illustrated in FIG. 6B, giving the possibility toobtain six DOF without the use of Cardan joints. Here a second oradditional rack- and pinion arrangement 293, 294 is introduced, wherethe pinion 294 is used to rotate the tool 28 via a right-angle gear 288.Also, one pinion 294 of the at least one second orientation transmission293/294 is connected to the tool 28 via the right-angle gear 288. Thesame principle as for the rack-and pinion arrangement 270 and 271 can beused to slide the rack 293, but the connection to a transmission to theactuator on the robot stand (not shown in the figure) is now insteadmade through the first gear wheel 64A. Thus, a link is connected to thebeam 297 that will move by translation the shaft 275 back and forth viathe bearing 296. The shaft 275 will move freely inside the bearing 66,the shaft 65 and the first gear wheel 64A and connect to the rack 293via the beam 295. Both rack- and pinion arrangements will be mounted onthe first gear wheel 64A, and as in FIG. 6B the shaft 65C is mounted viathe bearing 291 and the beam 290 to the pinion 270. For clarity thelinear bearings of the racks 271 and 293 are not shown, but these aremounted on a platform (not shown) to be rotated by the first gear wheel64A. The pinions 270 and 294 are mounted with bearings on the sameplatform and the shaft 65 can rotate freely inside the bearingsupporting the pinion 270. The right-angle gear assembly 288 is mounted(not shown) on the pinion 270. Thus, rotating the gear wheel 64A willrotate the tool (and the whole rack- and pinion transmissions) aroundthe axis 71, moving the beam 266 will rotate the tool 28 around thecenter of the shaft 65, which is at a right angle of the axis 71 andmoving the beam 297 will rotate the tool 28 around the rotation centerof the shaft 65C.

One shortcoming with the arrangement in FIG. 7 is that a rotation of thetool 28 around the center of the shaft 65 will simultaneously rotate thetool 28 around the center of the shaft 65C because of the functionalityof the right-angle gear 288. To avoid this, a third rack- and pinionarrangement can be introduced according to FIG. 8.

FIG. 8 illustrates an embodiment with three rack- and pinionarrangements to be rotated by a gear wheel 64A to completely avoid rightangle gears and Cardan joints in a six DOF robot. One of the rack- andpinion arrangements comprises two racks with a common pinion, where theracks are mounted at right angles relative each other. Here, theright-angle gear 288 of FIG. 7 has been replaced by a rack- and pinionarrangement 315, 316. The pinion 316 rotates the tool via the shaft 65Cand the rack 315 is connected to the rack 313 via the shaft 65 and thebearing 314. The rack 313 shares the pinion 312 with the rack 311, whichis connected to the shaft 275 via the beam 310. Thus, moving the beam297 will move the shaft 275 via the bearing 296 and then the rack 311.Moving the rack 311 will via the pinion 312 move the rack 313 at a rightangle to the movements of the rack 311. In other words, one rack- andpinion gear transmission 311, 312, 313 here comprises two racks 311, 313connected via a common pinion 312 and the two racks 311, 313 arearranged to move at right angle relative to each other. Then the rack315 will be moved by the freely moving shaft 65 via the rack bearing314. In other words, the rack shaft 65 is arranged to move freely in anaxial through hole of a pinion 270 belonging to another rack-and piniontransmission 270, 271. The rack 271 is moved in the same way as in FIG.6B via the rack attachment 287 and the rack bearing 267. The two racks313, 315 may be connected to each other via a rack shaft 65 and a rackbearing 314. Thus, this solution makes it possible to obtain six DOFmovements of the robot arm 500 with all actuators on the robot stand andwithout any coupling between the rotation axes of the tool. In otherwords, the robot arm comprises at least one further actuator and atleast one further kinematic chain configured to transmit a movement ofthe at least one further actuator to a corresponding movement of theend-effector arranged onto the end-effector platform, which gives atleast six degrees of freedom for the end-effector motion. As can be seenin the figure, the shaft 65C, rotating the tool 28, is mounted on thelower side of the pinion gear wheel 316. However, it can as well bemounted on the upper side of the pinion 316 and it is also possible tohave one tool mounted with a shaft on the upper side of pinion 316 andsimultaneously have another tool mounted on the lower side of the pinion316. The arrangement of FIG. 8 mounted on the main structure for axis1-3 and with the orientation transmission 64A, 64B and with three (3)parallel link transmissions and actuators for axes 4-6 can be furtherdeveloped to a 7 degrees of freedom robot by means of an actuatorrotating the base with the actuators for axes 1-6. In applications withhygienic requirements or with dirty environment it is easier to protectthe assemblies for the wrist Axes 4, 5 and 6 if only rotating sealingare used. To seal the arrangement in for example FIG. 5, a sealing forlinear movements is needed for the rod 266. FIG. 9A, illustrating arobot arm 500 according to a sixth embodiment, shows a way to get aroundthis problem since here only a rotating sealing are needed. The way toobtain this feature is to implement a second rack and pinionarrangement, where the racks are connected and where the pinions havedifferent diameters giving a gear factor larger than one. With the sametransmission design as in FIG. 5 from the fifth actuator 250 to thevertical movements of the link 258, the pinion gear 302 is rotated viathe shaft 301 by the lever 300 with its tip mounted on the link 258 viathe ball- and joint socket 259. Thus, the pinion 302 of the fixed rack-and pinion transmission 302, 307 includes the lever 300, on which a gearlink 258 is mounted via a joint 259 of at least two degrees of freedom.

The pinion gear wheel 302 is mounted on the shaft 301, which is mountedin the inner ring of the bearing 303. The outer ring of bearing 303 ismounted with the beam 304 on the linear bearing assembly part 305, whichin turn is mounted on the shaft 63 and thus firmly fixed to theend-effector beam 41. Thus, at least one rack bearing 267, 297 isconnected to the fifth actuator 250 via a fixed rack- and piniontransmission 302, 307 mounted on the end-effector platform 41. When thepinion gear wheel 302 rotates, the rack gear will move horizontally andbecause of the rigid coupling obtained by the beam 308 also the rackgear 271 will move horizontally. The beam 308 is connected to the rackgear 271 via the shaft 309 and the bearing 267. Also, the rack bearing267, 297 connected to the rack 307 of the fixed rack- and piniontransmission 302, 307. The shaft 309 is mounted in the inner ring of thebearing 267 and the outer ring of the bearing 267 is mounted on the rackgear 271. In one embodiment, the diameter of the pinion gear wheel 302is about three times larger than the diameter of the pinion gear wheel270 to obtain at least 360 degrees of rotation of the tool 28. Thus,FIG. 9A illustrates an alternative transmission to the link- and leverarrangement 260, 262, 264 in FIG. 5. Here a second rack- and pinion gearis connected in series with the rack- and pinion gear shown in FIG. 5.In this way a simpler arrangement of links and levers can be used withonly one link 258 and two levers 256 and 300. Thus, the robot arm 500comprises a fifth actuator 250 and a fifth kinematic chain configured totransmit a movement of the fifth actuator 250 to a correspondingmovement of the tool mounted to the end-effector platform 41 via thefirst gear wheel 64A. The fifth kinematic chain here comprises at leastone rack bearing 267, 297 connected to the fifth actuator 250 via a linktransmission 251, 258, 264.

FIG. 9B illustrates an alternative orientation linkage according to someembodiments. The orientation linkage gives the option to use a 90degrees gear 256A in order to rotate the axis 256B and lever 256 aroundan axis perpendicular to the center axis of the inner-arm assemblage 1.This will increase the working range of the transmission between thelever 256 and the gear transmission.

As understood from the disclosure, in some embodiments, the robot armcomprises a plurality of orientation linkages 52, 57, 59; 202, 204, 207,209; 251, 256, 258. Each orientation linkage has a connected orientationtransmission 64B, 64A, 216; 64C, 64D, 64E; 100, 64A; 260, 262, 264, 266,271, 270, respectively. The plurality of orientation linkages isconfigured such that each corresponding end-effector orientation isaccomplished for one or several end-effectors that are arranged onto theend-effector platform

FIGS. 10A, 10B illustrate a robot arm 500 according to a seventhembodiment, with a horizontal common first axis of rotation 29 of therotary actuators. The robot arm 500 is divided into FIGS. 10A and 10B tomake the understanding of the kinematic structures easier. Thus, FIG.10A shows the complete robot structure with the kinematic chain tocontrol the tilting angle of the tool 28. In this case the tool 28 isrotated by a lightweight rotating actuator 390, mounted on thehorizontal shaft 65 connected to the gear wheel 61B. The gear wheel 61Bis engaged by the gear wheel 64B, mounted on the shaft 213, which isconnected via the bearing 214 to the end-effector beam 41A. Theend-effector beam 41A is in this case part of an end-effector platform41 including the elements 366 together with the beam 68 which is hollow,in which the shaft 65 is mounted with one bearing in each end of thehollow beam 68. The end-effector platform 41 including the elements 366forms a rigid framework with rods mounted together to give support tothe joints 367, 368 and 369, the bearing 214 and the shaft 65. The shaft213 is rotated by a lever 61, which is connected to the end-effectorrotation link 59 by a ball- and socket joint 60. The end-effectorrotation link 59 is arranged to be moved up and down by a lever 257,which is connected to the end-effector rotation link 59 via a ball-andsocket joint 58. The lever 257 is arranged to be rotated to swing up anddown by the shaft 52, which is mounted on the bearings 53 and 55, whichin turn are mounted on the inner arm-assemblage 1 with the beams 53 and56. The shaft 52 is arranged to be rotated by the rotating actuator 50via the 90 degrees angle gear 51.

In this design shown in FIGS. 10A, 10B, the constraint on the tiltingdegree of freedom around the axis center of the end-effector beam 41A isobtained by a third link 365, connected to the end-effector platform 41with the ball-and socket joint 367A and to the inner arm-assemblage 1with the ball- and socket joint 367B. The first link 17 is connected tothe end-effector platform 41 with the joint 368 and to the innerarm-assemblage 1 with the joint 15 and link 18 is connected to theend-effector platform 41 with the joint 369. As can be seen in FIG. 7B,where the transmission for the control of the tilting angle has beenremoved for clarity, the upper end of the actuating link 18 of the outerpair of links is connected via the bearing 16C to the bearing pair 16Aand 16B. The rotation center of the bearing 16C coincides with the axiscenter of the actuating link 18. The bearings 16A and 16B are mounted onthe bearing 364 in such a way that the rotation axes of the bearings 16Aand 16B coincide and are at a right angle to the rotation angle of thebearing 363. The bearing 363 is mounted on the shaft 363, which in turnis mounted on the inner arm-assemblage 1 via the beam 364. Now the lever362 in the center of bearing 16A and connected to the outer ring of thebearing 363 is used to swing the bearing pair 16A, 16B around thebearing 363 and as a result the actuating link 18 will swing around thelever 362, which is parallel with the center of the hollow link of theinner arm-assemblage 1. The shaft 363 is actuated to swing up and downby the link 360, which has ball- and socket joints 359 and 361 in eachend. The joint 359 is connected to the lever 358, mounted on the outerring of the bearing 356. The inner ring of the bearing 356 is mounted onthe beam 357, in turn mounted on the inner arm-assemblage 1. Anotherlever 355 is mounted on the outer ring of the bearing 356 in a directionwhich is about 90 degrees relative the lever 358. The lever 355 isconnected to the link 353 via the bearing 354, which could actually alsobe a ball-and socket joint. The other end of the link 353 is connectedto the lever 351 via the bearing 352. The bearing 352 can also bereplaced by a ball- and socket joint. The lever 351 is forced to swingby a rotating actuator 350. In some applications this transmission toswing the link 18 is better than the using the first rotating shaft 3 asin previous figures. Examples are when the inner arm-assemblage 1 isvery long and it is easier to obtain stiffness in a link 353 with onlyaxial force instead of a shaft 3 with rotational torque.

Another new feature introduced in these figures is to use pairs of links11A, 11B and 12A, 12B instead of single links 11 and 12 as in theprevious figures. This makes it possible to use simple pairs of ball-and socket joints, which are kept together with springs between thelinks in the link pairs. Thus, the link system here comprises a thirdlink 365, the inner arm-linkage comprises a pair of parallel pairs ofparallel links 11A, 11B and 12A, 12B and the actuation of the tiltingangle of the tool 28 is now made via a link 353 which takes only axialforces. In other words, the links of the inner arm-linkage (the innerpair of parallel links 11, 12) comprises pairs of parallel links 11A,11B; 12A, 12B and these pairs of parallel links 11A, 11B; 12A, 12B aremounted with ball- and socket joints on each side of the links of theouter arm-linkage.

In the previous figures, hollow shaft actuators have been outlined tomake the figures easier to understand. FIG. 11 shows how the actuationcould instead be made with standard motors without hollow shafts. FIG.11 is a cut of two actuators driving the hollow link 1A and the rotaryshaft 3. Both the hollow link 1A and shaft 3 are tubes, for examplemanufactured in carbon reinforced epoxy. Hollow link 1A is mounted onthe outside of the ring 424, which is assembled together with thehousing 417. This housing is mounted on the shaft 416, which is rotatedby the motor 412 via the shaft 413 and the gear wheels 414 and 415. Thegear wheel 415 is mounted directly on the outer surface of shaft 416 andthe gear wheel 414 is mounted at the end of the shaft 413. The shaft 413is equipped with the bearing pair 428 between the gear housing 430 andthe shaft 413. In the same way, the shaft 416 is equipped with thebearing pair 426 between the gear housing 430 and the shaft 416.

The shaft 3 is mounted between the inner short shaft 422 and the outerring 423. The outer ring is in turn mounted in the housing 417 via thebearing 425 to support the rotation of shaft 3. In the other end shaft 3will be mounted with a corresponding bearing on the inside of the hollowlink 1A of the inner arm-assemblage 1. A 90 degrees gear wheel 421 ismounted on the short shaft 422. The gear wheel 421 is driven by the 90degrees gear wheel 420, mounted on the shaft 419, which is driven by themotor 418. The shaft 419 is supported by the bearing pair 427 betweenshafts 416 and 419. The first axis of rotation 29 (compare previousfigures) is defined by the rotation center of bearing 425 and thecorresponding rotation center of the bearing in the other end of shaft3. The first axis of rotation 29 (also shown in previous figures) isdefined by the rotation center of shaft 419. Thus, FIG. 11 illustratesan embodiment where the rotary actuators are arranged to obtain a commonrotation axis without using hollow shaft motors as illustrated in FIGS.1-6. The motors 412, 418 are mounted beside each other and hollow shaft416 gears 414, 415 are used.

FIG. 12A illustrates an alternative version of FIG. 1, where the firstaxis of rotation 29 of the actuators has been split into two differentparallel rotation axes 29A and 29B. In this way no hollow shaft actuatoris needed. Here the second actuator 5 is moved to have its own rotationaxis 29B and as before it is arranged to swing the lever 2 in order tomove the parallel links 11 and 12. The first actuator 4 and the thirdactuator 6 have a common rotation axis 29A. The first actuator 4 ismounted directly on the inner arm-assemblage 1 and the third actuator 6is connected to a right-angle gear not seen in the figure, to rotate theshaft 3. Simultaneously with the advantage that the actuator arrangementwill be simpler, there will be the drawback that the workspace will besomewhat reduced and the force transmission in the links 11 and 12 willdepend on the rotation angle of the inner arm-assemblage 1. In thefigures with more than three actuators it will of course also bepossible to have parallel rotation axes between different actuators. Forfurther description of FIG. 12A, reference is made to the description ofFIG. 1.

FIG. 12B illustrates that instead of an actuator (here the actuator 5)consisting of a rotational motor, possible a gearbox on the output motorshaft, and a lever (here the lever 2) that delivers the desired motionfor actuating each respective kinematic chain as in FIG. 12A, thedesired motion of link ends can be accomplished directly by a linearactuator. The function (to move joints 13 and 14) of the two links 11and 12 in FIG. 12A is accomplished by two ball-screws 811 and 812 thatend at joints 13 and 14 respectively, thereby providing the function oflinks 11 and 12. The ball-screws 811 and 812 are in the other endconnected to the beam 8, here via universal joints 809 and 810, whichhave the same function as joints 9 and 10 but for best function of theball-screws not permitting rotation around each respective link 811 and812. Each ball-screw comprises a ball-nut part 811A, 812A that isrotationally fixed to its base end at 809, 810, and it is alsorotationally fixed relative to the screw part 811B, 812B as needed toaccomplish the linear motion, which is from the screw 811B, 812Bextending from the ball-screw part 811A, 812A, thereby making the link811 and 812 shorter or longer. Here, the actuator 5 is duplicated andbuilt into or attached to both 811A and 812A such that the screw 811B,812B turns. Here actuator 5 (FIG. 12A) is integrated into 811A and 812Aand hence not visible in the figure. In FIG. 12A the single actuator 5and lever 2 moves the beam 8, but in FIG. 12B the two ball-screw eachhave one actuator, and hence they have to move synchronized (by means ofthe mentioned control system) to keep the axes 30 and 31 parallel. Analternative embodiment would be to have the lever 2 rotating about axis29B but without the actuator 5, and instead have a ball-screw actingfrom a location near centerline 29A to the beam 8. This way, only oneball-screw would be needed. The ball-screws may also act from a location(not shown) on the hollow link 1A, then not propagating the forces tothe robot stand.

In general, another way of using linear actuators is to use them with alever to create a limited-range rotation. Specifically, it applies toall of the rotations exhibited by all actuators in all enclosed figuresexcept FIGS. 6A, 6B and 12B, that motions are created by a rotationalactuator, which normally according to existing robot practice has anunlimited rotational capability. With the disclosed robot arm, however,except the plurality of wrist motions in FIGS. 6A and 6B, there is noneed to have large-range actuators. Instead, according to the presentinvention, each actuator can be linear, arranged with suitable levers.Hence, apart from ball-screws, actuators can be pneumatic or hydraulictoo, for very low robot cost or for very high end-effector forcesrespectively.

A transmission as used herein may be a gear transmission such astraditional pinion-pinion or rack-pinion with actual gears but may bereplaced by other transmissions, which may be based on wires or belts ofequivalent function for either pinion-pinion or rack-pinion geartransmissions. As used herein, the term “transmission” means anytransmission of similar functionality as the types of gear transmissionsmentioned above.

FIG. 13 shows parts of the transmission for end-effector rotation ofFIGS. 1 and 3A, but here the gears 64A and 64B have been replaced bybelt wheels 64C and 64D connected to the belt 64E. For furtherdescription of the components in the FIG. 13, reference is made to thedescription of FIGS. 1, 3-3D. A belt transmission can sometimes be madewith simpler mechanics than a gear transmission. Moreover, if thetransmission is made in plastic material, a cheap belt transmission mayhave a longer life time than gear wheels made in plastic.

FIGS. 14A and 14B explains the use of the backhoe mechanism (see FIG.4B) for the second kinematic chain, according to some embodiments. FIG.14A first illustrates the backhoe as such with the connection bearingsstill placed around the rotational centerlines of the two links of theouter pair of parallel links 17, 18. The base bearing 803 of the backhoeis placed on part 1A of the inner arm-assemblage 1, which means that thebackhoe can operate via two links 805, 806 and universal joints 21, 22as in FIG. 3A. Placing the bearing 803 on shaft 3 for a more preferabledirection of forces over the connection bearings would require anotherway of keeping the rotational axes 31 and 32 parallel to axis 33, forexample by introducing an additional joint between 8 and 802 and anadditional link between 8 and 7C (this is not shown in the figures). Themotivation for the backhoe is to increase the working range of thesecond kinematic chain, and thereby the workspace for the robot arm 500.In particular, most SCARA robots have a working range of more than 180degrees for the second DOF. The robot design according to WO2014187486,on the other hand, is limited by the parallelograms it is based on forthe inner and outer arm linkages, and not capable of operation within adesired 180 degree range. The backhoe (introduced in FIG. 4B) can solvethis problem, thereby forming a differentiating feature in relation toWO2014187486.

The backhoe as applied as in FIG. 14A shows the basic principle with thebeam 8 now placed closer to the elbow, now with rotating with a lever802 around bearing 803 such that actuating forces over joints 9C and 10Care better directed as the arm is stretched out with increasing anglesaround the second axis of rotation 40 that intersects with the elbowjoint 161. This provides some increase of workspace, at leastconsidering capabilities for end-effector forces in the direction ofaxis 33, but it does not reach a competitive working range since astretched-out arm will reach singularities with the outer pair ofparallel links flipping around their axis of rotation as allowed bybearings 15C and 16C. Note that bearings 15A, 15B, 15C together areequivalent to joint 15 in earlier figures. That is, the link part 804 isnot the problem concerning the flipping; joint 15 is separated intosingle-DOF joints as an illustrative preparation for the solution asillustrated in FIG. 14B.

In FIG. 14B the backhoe is configured to act on the outer pair ofparallel links via the connection bearings 21, 22 being placed on theoffset part of the out arm-linkage. That is, the connection bearingswith their common rotational axis 31 no longer intersects with therotational axis of the outer par of parallel links 17, 18. Instead, theconnection bearings are each placed such that their inner bearing (asinner to bearing 21A in FIG. 3D) rotate around an axis that intersectswith the second axis of rotation 40. This design, with proper dimensionof the mentioned offset compared to link lengths, as the skilled personwill easily determine (finding that the offset—being the distancebetween axis 40 along axis 33 until intersecting with the rotationalaxis of the actuating link 18—shall be at least the length of theactuating link times sine of the maximum angle of the outer arm linkagerelative a plane with normal direction parallel to axis 40). With aproper offset (such as the length of the actuating link 18 times sin(x)where x is the maximum allowed rotation of the outer arm linkagerelative a plane with normal direction parallel to axis 40),singularities will be outside the workspace (with the permitted range inz-direction agreeing with the maximum allowed x as to be configured inthe control system), and the second kinematic chain can operate past themost outstretched position of the outer arm-linkage.

The present disclosure is not limited to the above-describedembodiments. Various alternatives, modifications and equivalents may beused. Principles shown in the different figures can of course becombined, not only for the specifically illustrated kinematic chain orembodiment, but also at other parts of the arm structure whereverapplicable and apparent for the skilled person. Therefore, the aboveembodiments should not be taken as limiting the scope of the invention,which is defined by the appending claims.

The invention claimed is:
 1. A robot arm for end-effector motion,comprising: a first actuator configured to rotate an innerarm-assemblage about a first axis of rotation, the inner arm-assemblagebeing connected to an outer arm-linkage pivotably arranged around asecond axis of rotation, the outer arm-linkage being connected to anend-effector platform, thereby forming a first kinematic chain from thefirst actuator to the end-effector platform that provides a first degreeof freedom for positioning the end-effector platform; a second actuatorconfigured to rotate the outer arm-linkage around the second axis ofrotation, thereby forming a second kinematic chain from the secondactuator to the end-effector platform that provides a second degree offreedom for positioning the end-effector platform; a third actuatorconfigured to rotate a shaft around a third axis of rotation such thatthe outer arm-linkage is rotated via a joint, thereby forming a thirdkinematic chain from the third actuator to the end-effector platformthat provides a third degree of freedom for positioning the end-effectorplatform; and a fourth actuator and a fourth kinematic chain configuredto transmit a movement of the fourth actuator to a correspondingorientation axis for an end-effector, the fourth kinematic chaincomprising: an orientation linkage mounted to the inner arm-assemblagevia at least one bearing; and an orientation transmission mounted to theend-effector platform, wherein the orientation linkage comprises anend-effector rotation link and a plurality of joints that provide atleast two degrees of freedom for motion of each end-joint of theend-effector rotation link.
 2. The robot arm according to claim 1, wherethe orientation transmission comprises a connection to the end-effector,thereby providing at least four degrees of freedom for motion of theend-effector.
 3. The robot arm according to claim 1, where theorientation transmission comprises at least one outer gearing mechanismhaving a first gear ratio and arranged for rotating the end-effectorwithin an angular range that is determined by the first gear ratio ofthe outer gearing mechanism.
 4. The robot arm according claim 1, wherethe orientation linkage comprises at least one inner gearing mechanismhaving a second gear ratio and arranged for rotating the end-effectorwithin an angular range that is determined by the second gear ratio ofthe inner gearing mechanism without being limited by the rotation of theouter arm-linkage.
 5. The robot arm according to claim 1, where theorientation linkage and the orientation transmission are arranged forrotating the end-effector around the orientation axis without rotationalangular limits.
 6. The robot arm according to claim 5, furthercomprising a plurality of orientation linkages, each of the orientationlinkages comprising an orientation transmission, wherein the pluralityof orientation linkages is configured such that a correspondingplurality of concentric output shafts is operable to actuate severalend-effector orientations for at least one end-effector arranged ontothe end-effector platform.
 7. The robot arm according to claim 1,wherein the second kinematic chain comprises the inner arm-linkageincluding at least one link connected to the outer-arm linkage via aplurality of connection bearings, and wherein the second actuator isconfigured to move the at least one link via at least one innerconnection joint connected to the at least one link.
 8. The robot armaccording to claim 7, wherein the outer arm-linkage comprises an outerpair of parallel links connected to the end-effector platform, whereinthe inner arm-linkage comprises an inner pair of parallel links that areconnected to the outer pair of parallel links of the outer arm-linkage,and wherein the second kinematic chain is configured to transmitrotation of a lever to a corresponding movement of the end-effectorplatform.
 9. The robot arm according to claim 8, wherein the outer pairof parallel links and the inner pair of parallel links are connected bya connection bearing for each link connection of the respective links,and wherein each of the connection bearings has a rotation axis at aright angle to an axial centerline of each respective link of the outerpair of parallel links.
 10. The robot arm according to claim 9, furthercomprising a rigid beam connecting the connection bearings to eachother.
 11. The robot arm according to claim 10, where the inner pair ofparallel links is mounted via ball-and-socket joints on offset beams tothe rigid beam.
 12. The robot arm according to claim 8, wherein thethird kinematic chain comprises an inner transmission connected betweenthe third actuator and an actuating link of the outer pair of parallellinks.
 13. The robot arm according to claim 8, further comprising a linkbearing mounted along an actuating link of the outer pair of parallellinks, wherein the link bearing has an axis of rotation that coincideswith a center of the actuating link of the outer pair of parallel links.14. The robot arm according to claim 8, further comprising anend-effector bearing connecting each of the outer pair of parallel linksto the end-effector platform, wherein each of the end effector bearingshas a rotation axis that is perpendicular to a center of one of theouter pair of parallel links.
 15. The robot arm according to claim 14,wherein each of the connection bearings has a rotation axis, and whereinthe rotation axes of the end-effector bearings are parallel with therotation axes of the connection bearings.
 16. The robot arm according toclaim 8, further comprising a connection bearing connecting each of thelinks of the outer pair of parallel links to each of the links of theinner pair of parallel links, wherein a rotation axis of each connectionbearing coincides with a center of the respective link of the outer pairof parallel links.
 17. The robot arm according to claim 8, wherein eachof the links of the inner pair of parallel links comprises a pair ofparallel links mounted with ball-and-socket joints on each side of thelinks of the outer pair of parallel links.
 18. The robot arm accordingto claim 1, wherein the inner arm-assemblage comprises a hollow arm linkand the shaft mounted axially with bearings inside the hollow arm link,the shaft being rotatable by the third actuator.
 19. The robot armaccording to claim 1, wherein the fourth kinematic chain comprises aplurality of orientation linkages each connected to an orientationtransmission, wherein each of the orientation linkages and its connectedorientation transmission is configured such that a correspondingend-effector orientation is accomplished for at least one end-effectorarranged onto the end-effector platform.
 20. The robot arm according toclaim 1, further comprising at least two orientation transmissionsmounted to the end-effector platform, and wherein an outer gearingmechanism of one of the at least two orientation transmissions isarranged to rotate at least the other one of the at least twoorientation transmissions.
 21. The robot arm according to claim 1,further comprising a fifth actuator and a fifth kinematic chainconfigured to transmit a movement of the fifth actuator to acorresponding movement of the end-effector arranged onto theend-effector platform via at least one other orientation transmission.22. The robot arm according to claim 1, comprising at least one furtheractuator and at least one further kinematic chain configured to transmita movement of the at least one further actuator to a respective movementof the end-effector arranged onto the end-effector platform, therebyproviding at least six degrees of freedom for motion of theend-effector.